Supply -q (quiet mode) when bin/wp script calls vagrant ssh

When a script makes several calls to `bin/wp` from the host machine, each call is followed by:

> Connection to 127.0.0.1 closed.

This isn't helpful and can interfere with scripts which work with the output of `wp` calls. By supplying the `-q` (quiet mode) argument to `vagrant ssh`, this can be suppressed from being output with each WP-CLI command.