Refactor: tools: Use cib__signon_query() in crm_mon.c:cib_connect()

...and rename to setup_cib_connection() to avoid looking like a public
API function.

There is one small side effect of this change: cib__signon_query()
creates a read-write connection, while the existing code creates a
creates a read-only connection. In practice, I don't expect this to
matter.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>