current dhcpd.conf requires linux-host-entries.ttyS1-9600, add one

this file is not in puppet, current contents on brewster are search1-12 plus
searchidx1 (wiped and decommed, see rt 2897), so adding an
empty file.

Change-Id: I8d928aa307f17ed6abdbfba9232fd98f6eb11f50
Merge "current dhcpd.conf requires linux-host-entries.ttyS1-9600, add one" into production