fix Workgroup being overwritten by realm name. bnc#902302

don't set the Workgroup with the name returned from Samba.GetWorkgroupOrRealm
otherwise for non ADS config the realm/domain name will be set for Workgroup.

(cherry picked from commit e937ddd80d14d606e1916689a96843d525b87733)

Conflicts:
	package/yast2-samba-client.changes
	package/yast2-samba-client.spec