allow modem image to do OTA

Bug: 183174452
Test: run ./system/update_engine/scripts/update_device.py path/to/oriole-ota-*.zip
exit with status 0

Change-Id: I21a1cfcdf29eae1e06ed922cc44c1ff5b2916144
diff --git a/conf/fstab.gs101 b/conf/fstab.gs101
index 1ef1f79..281bc1e 100644
--- a/conf/fstab.gs101
+++ b/conf/fstab.gs101
@@ -13,7 +13,7 @@
 /dev/block/platform/14700000.ufs/by-name/efs             /mnt/vendor/efs             ext4    defaults,noatime,rw      wait,check,formattable
 /dev/block/platform/14700000.ufs/by-name/efs_backup      /mnt/vendor/efs_backup      ext4    defaults,noatime,rw      wait,check,formattable
 /dev/block/platform/14700000.ufs/by-name/modem_userdata  /mnt/vendor/modem_userdata  ext4    defaults,noatime,rw      wait,check,formattable
-/dev/block/platform/14700000.ufs/by-name/modem           /mnt/vendor/modem_img       ext4    ro,defaults,context=u:object_r:modem_img_file:s0    wait,slotselect
+/dev/block/platform/14700000.ufs/by-name/modem           /mnt/vendor/modem_img       ext4    ro,defaults,context=u:object_r:modem_img_file:s0,barrier=1    wait,slotselect
 /dev/block/platform/14700000.ufs/by-name/misc            /misc                       emmc    defaults                 wait
 /dev/block/platform/14700000.ufs/by-name/metadata        /metadata                   ext4    noatime,nosuid,nodev,data=journal,commit=1    wait,check,formattable,first_stage_mount,metadata_csum
 /dev/block/platform/14700000.ufs/by-name/pvmfw           /pvmfw                      emmc    defaults                 wait,slotselect,avb=pvmfw,first_stage_mount