sane-sync-from-iphone: handle the case where /mnt/iphone is hung

pkgs/sane-scripts/src/sane-sync-from-iphone

@@ -3,11 +3,16 @@
 set -ex
 
 # make sure the mountpoint exists
+if ! (test -e /mnt/iphone)
+then
+  sudo umount /mnt/iphone || true  # maybe the mount hung
+
   if ! (test -e /mnt/iphone)
   then
     sudo mkdir /mnt/iphone
     sudo chown colin:users /mnt/iphone
   fi
+fi
 
 # make sure the device is mounted
 if ! (test -d /mnt/iphone/DCIM)