monitoring lucene search boxes

Lucene search has a build in status report which can be accessed on
http://localhost:8123/status . Whenever an index has an issue it will
report FAILED, so we just have to look up for absence of that string
using check_http.

Tested on the beta instance:

 $ ./check_http  -H 127.0.0.1 -p 8123 -url=/status  --regex FAILED
--invert-regex
 HTTP CRITICAL: HTTP/1.1 200 OK - pattern found - 167799 bytes in 0.054
second response time |time=0.054401s;;;0.000000 size=167799B;;;0
 $

In production there are a few issues but the plugin seems to work fine
on all search servers.

Change-Id: I27516dc613a4b2f433ce156ba697c26ad4fe28f0
Merge "monitoring lucene search boxes" into production