Merge branch 'devel-2.2'

* devel-2.2:
  Add simple unittest for utils.CommaJoin
  LUDelTags: Improve formatting of error message
  LUGetTags: Acquire locks in shared mode
  gnt-cluster: Replace hardcoded “xenvg” with value retrieved from master
  Export VG name via LUQueryConfigValues
  RAPI QA: Override MAC address when moving instance
  move-instance: Allow overriding instance parameters
  cli: Move parsing of --net option to separate function
  kvm: collapse two consecutive extend calls
  kvm: Introduce support for -mem-path

Conflicts:
	test/ganeti.cli_unittest.py: Trivial

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>