ifcfg: Put hotplug=no for virtual devices

In el6 systems, udev can trigger an ifup call when a device is
created. The issue with the triggering is that when we create a
virtual device, e.g. a vlan, we do so via ifup, so what will
happen is:

we write ethX.Y
initscripts creates the
  vlan device with id Y
  on top of ethX.                      udev detects the new device
        | Process 1                              | Process 2
initscripts finished doing             udev calls initscripts' ifup
ifup, possibly calling dhclient            for the new vlan device
                                       initscripts possibly calls
                                           dhclient

The issue is that the two processes can do the dhclient in whichever
order and one dhclient will prevent the other from succeeding. Only
one ifup should be called for each device, so we need hotplug=no to
prevent Process 2 from succeeding in its ifup.

Our current usage of ifcfg files does not set hotplug=no
so that when the user replaces a physical card by hot-unplugging
and hot-plugging there will be an auto configuration. This behavior
is maintained by the fact that we only set hotplug=no for those
devices for which we control the whole life cycle, i.e., vlans,
bonds and bridges.

Bug-Url: https://bugzilla.redhat.com/1097818
Change-Id: I6a60bb8d461572855c951fff8c991e34e0feb332
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/27980
Reviewed-by: Dan Kenigsberg <danken@redhat.com>