Add ansible executable path (argv[0]) to --version (#22262)

For example:

    ansible 2.3.0 (argv0_in_version f53921093f) last updated 2017/03/03 13:33:31 (GMT -400)
      config file = /home/adrian/.ansible.cfg
      configured module search path = Default w/o overrides
      executable location = /home/adrian/src/ansible/bin/ansible

This should help troubleshooting install issues.

lib/ansible/cli/__init__.py

@@ -485,6 +485,7 @@ class CLI(with_metaclass(ABCMeta, object)):
             cpath = C.DEFAULT_MODULE_PATH
         result = result + "\n  configured module search path = %s" % cpath
         result = result + "\n  ansible python module location = %s" % ':'.join(ansible.__path__)
+        result = result + "\n  executable location = %s" % sys.argv[0]
         result = result + "\n  python version = %s" % ''.join(sys.version.splitlines())
         return result