Fixed spurious MDSAL commit tests failures.

The fixed "commit" operation always returns OK when the
candidate configuration is exactly the same as the running
configuration. Which makes sense as the commit's task is to
turn the running configuration to be exactly the same as the
(currently present) active configuration. However the tests
were expecting the commit to fail in this situation and thus
are now producing spurious failures.

Change-Id: I2f25e3d53a9519a5987e386e7ebe4d7161c0b767
Signed-off-by: Jozef Behran <jbehran@cisco.com>