crowbar_join: Try longer to ping the admin server

Apparently, on some hardware, the network card takes 20 seconds to be
up, so just one initial ping is not a good enough test. Let's try for
two minutes.

https://bugzilla.novell.com/show_bug.cgi?id=871460
(cherry picked from commit 89be5f01fd790de72d59079cd1176c300a47cd92)
crowbar_join: Get the hostname before pinging the admin server

(cherry picked from commit 7437ddd5327fd95b4fec9dcdd8ed31a0375f286c)
crowbar_join: Do not sleep if we're going to fail anyway

(cherry picked from commit 28add36baf47cb003f94e2c29de6881389c4bc89)