Disable pseudo-TTY allocation for getting the URL in `test_deploy`.

Added `ssh -T` flag when getting url from dokku command over ssh since
without it, the returned string cannot be appended to correctly. For
example:
- (with PTY): :8080//test-nodejs-express-10694.dokku.me
- (disable PTY): http://test-nodejs-express-10694.dokku.me:8080