As Edison's system clock is not always synchronized, mounting time issues
may occur during file system check and block the boot.
By setting broken_system_clock to true in e2fsck.conf, e2fsck will not
abort a check if it detects a last mounted or last write time in the
superblock in the future.

Tracked-On: EDISON-2430
Signed-off-by: Rodriguez Fabien <fabienx.rodriguez@intel.com>