Fixed mounting /system when 'override_prop' is enabled.

Change-Id: I59f035498c2a2d65869cb7f7e6ea9e311b9757be
Revert "Revert "Revert "Revert "Here we come, 4.9""""

This reverts commit 62e2b363e8bbee56b13c078a7acf6c1377373164.
Merge branch 'cm-11.0' of https://github.com/CyanogenMod/android_build into cm-11.0