Revert to TCP as the default protocol

[shueybubbles]

The named pipe dialer treats ERROR_FILE_NOT_FOUND as a signal to keep retrying until the timeout elapses.
I have a PR at natefinch/npipe#35 to enable a way for go-mssqldb to fail quickly but I don't think that repo is still active for PRs.

For now we will default to TCP, and if the PR languishes I will write our own named pipe dialer in go-mssqldb.