Fixed device or resource busy issue in EXIT trap

cleanup for ramdisk failed to umount TMP_BUILD_DIR with device or
resource busy error.

The patch unmounts all the mountpoints under TMP_BUILD_DIR and
detaches loop devices associated with TMP_IMAGE_PATH.

The unmounts are applied with both force(-f) and lazy(-l)
options. Force option is only for NFS mounts, it's kept here since no
harm for lazy option.

Change-Id: I84035e6a003d8135186b2fda3facbd2c37967529

lib/common-functions

@@ -275,3 +275,12 @@ function mount_proc_dev_sys () {
     sudo mount -t sysfs none $TMP_MOUNT_PATH/sys
 }
 
+function unmount_dir () {
+    local pattern="$1" mnts=""
+    if [ -n "$pattern" ]; then
+        mnts=`awk '{print $2}' < /proc/mounts | grep "^$pattern" | sort -r`
+    fi
+    if [ -n "$mnts" ]; then
+        sudo umount -fl $mnts || true
+    fi
+}

lib/ramdisk-functions

@@ -25,7 +25,14 @@ function fullpath() {
 }
 
 function cleanup () {
-  sudo umount -f $TMP_BUILD_DIR || true
+  unmount_dir "$TMP_BUILD_DIR/mnt"
+  if [ -f "$TMP_IMAGE_PATH" ]; then
+    loopdev=`sudo losetup -j "$TMP_IMAGE_PATH" | cut -d: -f1`
+    if [ -n "$loopdev" ]; then
+      detach_loopback "$loopdev"
+    fi
+  fi
+  unmount_dir "$TMP_BUILD_DIR"
   rm -rf --one-file-system "$TMP_BUILD_DIR"
 }