bug 938061 - final  - r=zac

Conflicts:
	tests/python/gaia-ui-tests/gaiatest/tests/functional/system/manifest.ini
Merge pull request #14464 from AndreiH/bug938061_v1.2

bug 938061 - final  - r=zac
Bug 944276: MMS workaround for problem with memory-backed blobs

fix failing test and address review comments