It's better for daemons if:
  - they log only to one log file
  - the log level is included
  - for debug runs, the filename/line number is included

This patch moves the custom formatter from the watcher to the logging
module and generalizes it; then it changes the master daemon to use this
function instead of the generic logging (which might be deprecated
anyway in the future).

Reviewed-by: imsnah

Reviewed-by: iustinp

This is the safest way to detect changes and the amount of data
is small, so keeping a copy around is cheap enough.

Reviewed-by: iustinp

Cleanup: _data is private and should not be modified from outside
of this class.

Reviewed-by: iustinp

Reviewed-by: iustinp

- Lock it before renaming
- Code cleanup; close() automatically unlocks it

Reviewed-by: iustinp

Reviewed-by: iustinp

Reviewed-by: ultrotter

- Log timestamp for all messages
- Write everything to logfile and optionally to stderr
- Log messages are no longer buffered, allowing a user to see progress

Reviewed-by: ultrotter

Currently the watcher runs first the instance startup and then the
boot-id method of disk reactivation. However, irrelevant of the fact
that a node has rebooted or not, if we just started an instance, there's
no need for its disks to be activated again, since the start instance
has done that (if it is at all possible).

The patch modifies the watcher to remember all started instances and not
run activate-disks for them.

Reviewed-by: ultrotter

Currently the watcher does activate disks (via bootid mechanisms) even
for admin_down instances.  This patch logs and skips over these
instances.

Reviewed-by: ultrotter

This patch modifies the watcher to run the ‘gnt-cluster verify-disks’
command and to log its output (if any).

Reviewed-by: imsnah

- When line wrapping is needed, move spaces to the next line.
- Remove embedded line breaks from error messages.

Reviewed-by: schreiberal

- Use constants for keys.
- Fix bug through which automatic instance restarts wouldn't be limited

Reviewed-by: iustinp

Reviewed-by: iustinp

- Change format of watcher state file to JSON.
- Move log path for watcher script to constants.py.

Reviewed-by: iustinp

We currently require that hostnames are FQDN not short names
(node1.example.com instead of node1). We can allow short names as long
as:
  - we always resolve the names as returned by socket.gethostname()
  - we rely on having a working resolver

These issues are not as big as may seem, as we only did gethostname() in
a few places in order to check for the master; we already required
working resolver all over the code for the other nodes names (and thus
requiring the same for the current node name is normal).  The patch
moves some resolver calls from within execution path to the checking
path (which can abort without any problems). It is important that after
this patch is applied, no name resolving is called from the execution
path (LU.Exec() or other code that is called from within those methods)
as in this case we get much better code flow.

This patch also changes the functions for doing name lookups and
encapsulates all functionality in a single class.

The final change is that, by requiring working resolver at all times, we
can change the 'return None' into an exception and thus we don't have to
check manually each time; only some special cases will check
(ganeti-daemon and ganeti-watcher which are not covered by the
generalized exception handling in cli.py). The code is cleaner this way.

Reviewed-by: imsnah

This changes the raising of exceptions from:
  raise Exception, value
to
  raise Exception(value)

as the first form will be removed in python-3000 and the second form is
preferred now.

The changes also involve a few cases of changing from raising standard
exceptions and use our own ones.

The new version also fixes many pylint-generated warnings, especially in
ganeti-noded where I changed many methods to @staticmethod.

There is no functionality changed (barring any bugs).

Reviewed-by: iustinp

Reviewed-by: imsnah