As per the changes to LUQueryNodes, the QueryInstances LU is modified to
accept a list of instances for which to compute and return information.

Reviewed-by: imsnah

Now that LUQueryNodes supports all the functionality of LUQueryNodeData,
let's migrate gnt-node.ShowNodeConfig to use it and remove all traces of
OpQueryNodeData and LUQueryNodeData.

Reviewed-by: imsnah

LUQueryNodes it's very similar to LUQueryNodeData, but it lacks two
features:
  - instance list (it has count though), both primary and secondary
  - selective node listing

In order to support these features, we change it to return raw values
instead of stringified ones (like the recent change to LUQueryInstances)
and to support query-ing of a restricted set of nodes.

This CL also modifies the gnt-node script to conform to the new protocol
and the opcode OpQueryNodes to support the new "nodes" attribute.

Reviewed-by: imsnah

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).

This is only the backend part, from the command line the tags can't be
read/modified yet.

Reviewed-by: imsnah

- Add the command to gnt-instance.sgml

Reviewed-by: iustinp

- Implement “gnt-instance reinstall”
- Fix two typos

Reviewed-by: iustinp

- Create all --output options using a constant
- Put node checking code from opcodes into a single function
- Do the same for output fields

Reviewed-by: iustinp

  - move the master node name from the ConfigWriter to SimpleStore (all
    nodes need this, and it was the only thing pulled in from the
    ConfigWriter on nodes)
  - fix mcpu.py and the testing w.r.t. this change; for testing, rename
    the fake_config.py to mocks.py and add a FakeSStore object
  - then add a ganeti-master script which can be run on any node at boot
    and which will not do anything if not master on start (on stop it
    will still try to remove the ip address)
  - also add a new cluster-wide variable (master_netdev) that determines
    on which interface we add this ip address; it's customizable at
    cluster init time
  - also remove the cluster name file which was separately handled from
    ssconf (not needed anymore)
  - remove the master init.d links from the list of config files as this
    is not our responsibility now