Support for -a to accept a file with test-module

If the CLI value for -a starts with an @, treat it like a file, and dump the contents into complex_args

This supports yaml or json.

hacking/test-module

@@ -89,6 +89,11 @@ def boilerplate_module(modfile, args, interpreter):
     #included_boilerplate = module_data.find(module_common.REPLACER) != -1 or module_data.find("import ansible.module_utils") != -1
 
     complex_args = {}
+    if args.startswith("@"):
+        # Argument is a YAML file (JSON is a subset of YAML)
+        complex_args = utils.combine_vars(complex_args, utils.parse_yaml_from_file(args[1:]))
+        args=''
+
     inject = {}
     if interpreter:
         if '=' not in interpreter: