Fix package names for rhel/centos using ads security

RHEL/CentOS use krb5-workstation instead of krb5-user as well
as samba-winbind instead of winbind package names.
samba-common winbind package for rhel5
Removed extreneous closing parenthesis
Merge pull request #15 from tomas-edwardsson/rhel6ads

Fix package names for rhel/centos using ads security