Altering indexer config to properly match on libvirtd files

The tags associated with libvirtd.txt in logstash are libvirtd.txt
and libvirt, the index config looked for libvirtd as the current
setup does not appear to match - we only have {%logmessage%} for message
content now. Setting search tag to 'libvirt'.

Change-Id: I27ae3b034581571285f42dab674ed85ff820cb6f
Partial-bug: 1350121
Merge "Altering indexer config to properly match on libvirtd files"