scripts/combo-layer: avoid saving last revision if unchanged
If we are running an update and the last revision hasn't changed since
the last update, don't write to the configuration file. This avoids
committing the config file with no changes other than spontaneous
reordering of sections, which sometimes occurs due to the behaviour of
the internal dictionary in Python's ConfigParser class. (This can be
fixed properly but the fix is only easy in Python 2.7+ due to the
availability there of the collections.OrderedDict class, and we
currently want to be compatible with 2.6.x as well.)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
