releasetools: Fallback to "mkbootimg_args" if "recovery_mkbootimg_args" not found.

For older target_files.zip, since "recovery_mkbootimg_args" may not be
set fallback to the earlier config -"mkbootimg_args" for recovery image.
This will make releasetools backward compatible, and usable for
older/already generated target-files package.

Change-Id: If40359130b8e6da48cb8c345d8cb079f457fe36f
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 2f89a70..cdb10fa 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -1145,6 +1145,10 @@
 
   if partition_name == "recovery":
     args = info_dict.get("recovery_mkbootimg_args")
+    if not args:
+      # Fall back to "mkbootimg_args" for recovery image
+      # in case "recovery_mkbootimg_args" is not set.
+      args = info_dict.get("mkbootimg_args")
   else:
     args = info_dict.get("mkbootimg_args")
   if args and args.strip():