This fixes a crash with an error in the log file (see below) that
happened when the MongoDB authorization module queried the database. The
reason is that the collection name that was sent to the mongodb
connection was an atom. This is fixed by making sure it is not an atom.
2023-03-08T17:16:34.215523+01:00 [error] msg: query_mongo_error, mfa:
emqx_authz_mongodb:authorize/4, line: 95, peername: 127.0.0.1:53212,
clientid: client123, collection: mqtt_acl, filter: #{username =>
<<"emqx_u">>}, reason: {resource_error,#{msg => #{error =>
{error,{error_cannot_parse_response,{op_msg_response,#{<<"code">> =>
73,<<"codeName">> => <<"InvalidNamespace">>,<<"errmsg">> => <<"Failed to
parse namespace element">>,<<"ok">> => 0.0}}}},id =>
<<"emqx_authz_mongodb:3">>,name => call_query,request =>
{find,mqtt_acl,#{username => <<"emqx_u">>},#{}},stacktrace =>
[{mc_connection_man,reply,1,[{file,"mc_connection_man.erl"},{line,123}],
...]}, reason => exception}}, resource_id: <<"emqx_authz_mongodb:3">>
Fixes: https://github.com/emqx/emqx/issues/9783