crowbar_join.suse: Remember reboot request

Remember reboot request so crowbar can wait until the reboot finished.
This is done in crowbars run_remote_chef_client() function. The newly added
start handler resets the reboot state.

https://bugzilla.novell.com/show_bug.cgi?id=878012
Merge pull request #320 from toabctl/remember-reboot

crowbar_join.suse: Remember reboot request
add zypper no-gpg-checks flag
Merge pull request #321 from MaximilianMeister/no-gpg-checks-option

add zypper no-gpg-checks flag
crowbar_join.suse: Always install chef handlers

Install chef reboot handlers also if /etc/chef/client.rb is
already available.
crowbar_join.suse: Remember time before reboot

Store seconds since epoch before reboot in
node[:crowbar_wall][:wait_for_reboot_requesttime] and reset the variable with
the reboot reset handler. The variable can be used to verify that a
reboot already happened.
Merge pull request #322 from toabctl/reboot-handler-upgrade

crowbar_join.suse: Always install chef handlers
Disable probing of network interfaces

provides a significant speedup on running sudo on a larger
neutron deployment.

see http://www.sudo.ws/pipermail/sudo-workers/2014-January/000835.html