Merge branch 'stable-2.8' into master

* stable-2.8: (42 commits)
  Add shelltests for hspace allocation
  hspace: Handle multiple ipolicy specs
  QA: Test multiple instance specs
  QA: Handle multiple instance specs
  Unit test for cli.FormatPolicyInfo()
  Add command-line support for multiple specs in ipolicy
  Add multiple min/max specs in instance policy
  Separate checks for std spec compliance
  QA: Transpose instance specs
  Improve check for  "unreleased" versions in NEWS
  Update documentation for text format
  Add missing fields in htools text-backend documentation
  cfgupgrade: Remove enabled_disk_templates on downgrade
  Reason trail implementation for "start"
  Reason trail implementation for "shutdown"
  QA: More tests for instance policies in groups
  QA: Split function to set and parse instance policies
  QA: Update tests for new ipolicy specs command-line options
  Add unit tests for cfgupgrade with a real configuration
  Split functions in cfupgrade unit tests
  ...

Conflicts:
        lib/backend.py
        lib/bdev.py
        man/gnt-cluster.rst

lib/bdev.py was renamed to lib/block/bdev.py in master, so I've manually
applied the bc3427b7 commit to the new file. The other two are
straightforward conflicts.

Signed-off-by: Bernardo Dal Seno <bdalseno@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>