rpm: include the systemd units on RHEL7

In addition to the systemd unit, add the needed %post scripts so that
systemd gets informed about the new unit.

The parameters for ganesha.nfsd can be configured in
/etc/sysconfig/ganesha. This file already gets installed by the RPM, and
the SysV init-script uses it. The systemd unit has been updated to use
/etc/sysconfig/ganesha too.

Signed-off-by: Niels de Vos <ndevos@redhat.com>
rpm: include the nfs-ganesha-lock systemd unit

Signed-off-by: Niels de Vos <ndevos@redhat.com>
Acked-by: Philippe DENIEL <philippe.deniel@cea.fr>
Acked-by: Daniel Gryniewicz <dang@cohortfs.com>