[reclass] Ensure pxe_admin_address is set for all

[reclass] Ensure pxe_admin_address is set for all

Some nodes did not rely on the _param:pxe_admin_address internal
reclass param, although all of them do have an IP address in the
PXE/admin network segment.

Ensure all nodes define this param, so we can query all nodes with:
$ salt '*' pillar.item _param:pxe_admin_address

JIRA: FUEL-394

Change-Id: I7575934752c8b459c52af8a8c98c2b0327756428
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>
(cherry picked from commit a20ca2d8aaf550e1a1766768a2f4403a795d9e12)