Add ME_CONFIG_MONGODB_URL support to wait_tcp_port

[CodingKoopa]

This pull request adds support for parsing the ME_CONFIG_MONGODB_URL connection string in order to wait for the TCP port to be open.

I have extensively tested this with all of the possible URL combinations I could think of, but it's possible that I've missed some weird possibility. Please see this Gist for a Bash script using the same exact logic found in this PR, tested against various testcases.

Thanks!