title: sphinx index fail, and ask me to restart the server with query_cache_type=1 to enable it
body: <p>mysql config <code>my.ini</code> default query_cache_type=0 .<br>
  I have already set <code>sql_query_pre = SET SESSION query_cache_type=OFF</code> in <code>sphinx.conf</code>.I think it is not good to turn cache while indexing.But sphinx still asking me to turn on cache...</p>
  
  <p>error detail:</p>
  
  <p>win7 x64, sphinx 2.1.7</p>
  
  <pre><code>I:\sphinx\bin&gt;I:\sphinx\bin\indexer.exe --all --config I:\sphinx\bin\sphinx.conf
  Sphinx 2.1.7-id64-release (r4638)
  Copyright (c) 2001-2014, Andrew Aksyonoff
  Copyright (c) 2008-2014, Sphinx Technologies Inc (http://sphinxsearch.com)
  
  using config file 'I:\sphinx\bin\sphinx.conf'...
  indexing index 'test1'...
  ERROR: index 'test1': sql_query_pre[1]: Query cache is disabled; restart the server with query_cache_type=1 to enable it
   (DSN=mysql://root:***@localhost:3306/test).
  total 0 docs, 0 bytes
  total 0.018 sec, 0 bytes/sec, 0.00 docs/sec
  skipping non-plain index 'rt'...
  total 0 reads, 0.000 sec, 0.0 kb/call avg, 0.0 msec/call avg
  total 0 writes, 0.000 sec, 0.0 kb/call avg, 0.0 msec/call avg
  </code></pre>