fs_mgr: use different fstab paths for normal/recovery boot

  recovery boot: /etc/recovery.fstab
  normal boot: use the first one found by the order:
               /odm/etc/fstab.{hardware} ->
               /vendor/etc/fstab.{hardware} ->
               /fstab.{hardware}

Bug: 35811655
Bug: 36637553

Test: Sideload OTA installation in sailfish
Change-Id: I3e260e077afa5a37fb65246246c824e9379e68c8