Configure PoolCounter for search requests

Requires I1298bc70 to be live to function.
- Set workers to 78. Lucene has a thread pool of 80, so use most
  of them without overloading it.
- Set the max queue to 400. This is roughly half the possible requests that
  it would take to overload the apaches. 6 Lucene * 800 max queue = 4800
  processes, which is the number of regular apache processes in eqiad.
- Set wait timeout to 15s

Change-Id: Id425616f4fbc1397584e4c153b5b3c4712f85f16
Merge "Configure PoolCounter for search requests"