backuptool: Support tab-delimited fstab

Change-Id: Ib3fcde92d0c1ebb8754b11c577e4885d8dd02624

prebuilt/common/bin/backuptool.sh

@@ -104,7 +104,7 @@ unmount_system() {
 }
 
 get_block_for_mount_point() {
-  grep -v "^#" /etc/recovery.fstab | grep " $1 " | tail -n1 | tr -s ' ' | cut -d' ' -f1
+  grep -v "^#" /etc/recovery.fstab | grep "[[:blank:]]$1[[:blank:]]" | tail -n1 | tr -s [:blank:] ' ' | cut -d' ' -f1
 }
 
 find_block() {

prebuilt/common/bin/backuptool_ab.sh

@@ -95,7 +95,7 @@ fi
 ### Mount helpers ###
 #####################
 get_block_for_mount_point() {
-  grep -v "^#" /vendor/etc/fstab.$(getprop ro.boot.hardware) | grep " $1 " | tail -n1 | tr -s ' ' | cut -d' ' -f1
+  grep -v "^#" /vendor/etc/fstab.$(getprop ro.boot.hardware) | grep "[[:blank:]]$1[[:blank:]]" | tail -n1 | tr -s [:blank:] ' ' | cut -d' ' -f1
 }
 
 find_block() {