Simplify flask.cli.main

Werkzeug>=0.15's reloader now properly detects `python -m module`.
Fixes #3022

flask/cli.py

@@ -907,23 +907,7 @@ debug mode.
 
 
 def main(as_module=False):
-    args = sys.argv[1:]
-
-    if as_module:
-        this_module = "flask"
-
-        if sys.version_info < (2, 7):
-            this_module += ".cli"
-
-        name = "python -m " + this_module
-
-        # Python rewrites "python -m flask" to the path to the file in argv.
-        # Restore the original command so that the reloader works.
-        sys.argv = ["-m", this_module] + args
-    else:
-        name = None
-
-    cli.main(args=args, prog_name=name)
+    cli.main(prog_name="python -m flask" if as_module else None)
 
 
 if __name__ == "__main__":