Adds `action update` test that expects failure when missing file is specified

Removes deadcode from WskCLI.java.
diff --git a/tools/cli/wskaction.py b/tools/cli/wskaction.py
index d8b51a1..6571ead 100644
--- a/tools/cli/wskaction.py
+++ b/tools/cli/wskaction.py
@@ -87,7 +87,8 @@
     def create(self, args, props, update):
         exe = self.getExec(args, props)
         validExe = exe is not None and 'kind' in exe
-        if update or validExe: # if create action, then exe must be valid
+        fileok = args.artifact is None or os.path.isfile(args.artifact)
+        if (update and fileok) or validExe: # if create action, then exe must be valid
             payload = {}
             if args.annotation:
                 payload['annotations'] = getAnnotations(args)