ota_from_target_files: Fix path for SkipNextActionIfTargetExists

Without the leading forward slash, the check always fails.

Change-Id: I57320c20ca2b384713182082b1ad5321d78dbb2b
diff --git a/tools/releasetools/ota_from_target_files b/tools/releasetools/ota_from_target_files
index bde1c8f..000f103 100755
--- a/tools/releasetools/ota_from_target_files
+++ b/tools/releasetools/ota_from_target_files
@@ -1057,7 +1057,7 @@
     so_far = 0
     for tf, sf, size, patch_sha in self.patch_list:
       if tf.name != sf.name:
-        script.SkipNextActionIfTargetExists(tf.name, tf.sha1)
+        script.SkipNextActionIfTargetExists("/"+tf.name, tf.sha1)
       script.PatchCheck("/"+sf.name, tf.sha1, sf.sha1)
       so_far += sf.size
     return so_far
@@ -1087,7 +1087,7 @@
         deferred_patch_list.append(item)
         continue
       if (sf.name != tf.name):
-        script.SkipNextActionIfTargetExists(tf.name, tf.sha1)
+        script.SkipNextActionIfTargetExists("/"+tf.name, tf.sha1)
       script.ApplyPatch("/"+sf.name, "-", tf.size, tf.sha1, sf.sha1, "patch/"+sf.name+".p")
       so_far += tf.size
       script.SetProgress(so_far / total_patch_size)