Fix SD card mounting & switch to mount_all via fstab

Notes:
* Two copies of fstab are installed to rootdir, because a) system init
  can't parse ro.hardware property until /system is mounted; and b) the vold
  service checks for the /fstab.bootloader filename and nothing else.
* Moved new fstab to msm7x27-common and set TARGET_RECOVERY_FSTAB to point
  towards this file. You must remove other definitions/fstabs in per-device
  configs for this to work as intended. All Samsung fstabs are identical,
  so it belongs in the shared config.

Change-Id: Ic7b6ae8e36f10fac1c46e6ff7ce3382c66df7ec0