Fixed mounting /system when 'override_prop' is enabled.

Change-Id: I59f035498c2a2d65869cb7f7e6ea9e311b9757be
Edify: Add AssertSomeBaseband

Allow releasetools.py to assert a baseband version. Works just like
AssertSomeBootloader.

Change-Id: Ic8eb341cef1d777d983be25ba21a3bc545819c29
ota_from_target_files: Validate signatures after possible data wipe

If the data is being wiped, we want to validate the signature after
this step. This is also a good check that the data wipe succeeded.

Change-Id: Iaecfddfb2010944de0c97e7bb21d8e581f20deec
Merge remote-tracking branch 'cyan/cm-11.0' into cm-11.0