ctdb-scripts: Simplify TCP port checking

ctdb-scripts: Simplify TCP port checking

Commit 86792724a2a911da9cd3e75622d35084c88eb8ce added complications on
top of the multiple TCP port checking methods that used to exist.
Life is simpler now and the cause of any failures is obvious.  So just
print a simple message if the port check fails.

Tweak tests to match changes.  Drop one test that becomes a duplicate.

Temporarily tweak ctdb_check_command() so that it passes shellcheck
tests.  It will be removed anyway in a subsequent commit.

Signed-off-by: Martin Schwenke <martin@meltin.net>
Reviewed-by: Amitay Isaacs <amitay@gmail.com>