remove mount/unmount capabilities from backuptool

backuptool should not be messing with whether /system is mounted
or not as it screws up the expectations of other scripts run
in the install process. instead the mounting/unmounting
functionality has been moved to ota_from_target_files

Change-Id: I0711afd517638e7d0a0c39369d3a776748245dd2
diff --git a/prebuilt/common/bin/backuptool.sh b/prebuilt/common/bin/backuptool.sh
index fbedf93..6ba1323 100755
--- a/prebuilt/common/bin/backuptool.sh
+++ b/prebuilt/common/bin/backuptool.sh
@@ -7,20 +7,6 @@
 export S=/system
 export V=10
 
-# Mount /system if it is not already mounted
-mount_system() {
-if ! mount | grep -q " $S " ; then
-  mount $S
-fi
-}
-
-# Unmount /system unless it is already unmounted
-umount_system() {
-if mount | grep -q " $S " ; then
-  umount $S
-fi
-}
-
 # Preserve /system/addon.d in /tmp/addon.d
 preserve_addon_d() {
   mkdir -p /tmp/addon.d/
@@ -38,7 +24,6 @@
 check_prereq() {
 if ( ! grep -q "^ro.cm.version=$V.*" /system/build.prop ); then
   echo "Not backing up files from incompatible version."
-  umount_system
   exit 127
 fi
 }
@@ -53,22 +38,18 @@
 case "$1" in
   backup)
     mkdir -p $C
-    mount_system
     check_prereq
     preserve_addon_d
     run_stage pre-backup
     run_stage backup
     run_stage post-backup
-    umount_system
   ;;
   restore)
-    mount_system
     check_prereq
     run_stage pre-restore
     run_stage restore
     run_stage post-restore
     restore_addon_d
-    umount_system
     rm -rf $C
     sync
   ;;