fix bash ineffective timestamp

If we were to perform more than a setSafeNetworkConfig in a second
the timestamp would be the same and we'd explode by putting
    /var/run/vdsm/netconf inside the old
    /var/lib/vdsm/persistence/netconf.931247
like so
    /var/lib/vdsm/persistence/netconf.931247/netconf
instead of replacing it atomically.

Adding the nanoseconds to the timestamp makes collisions go away.

Change-Id: I2b4262b4fa242f20f55d03931d8c62b4650a34a1
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/20459
Reviewed-by: Dan Kenigsberg <danken@redhat.com>