testapp.cc: Fix Clang Analyzer false positive (FD_ZERO)
testapp.cc: Fix Clang Analyzer false positive (FD_ZERO)

As reported by Clang Static Analyzer:

    File:	 testapp.cc
    Location:	 line 3579, column 5
    Description: The result of the '<<' expression is undefined

Note this is a false positive - FD_ZERO() is guaranteed to
zero-initialize the file descriptor set, however some implementations
(Ubuntu 12.04 at least) use inline asm for this which Clang cannot
parse, and hence incorrectly believes that fdset is uninitialized.

Solve by simply #ifdef'ing the FD manipulating code out when run under
Clang analyzer.

Change-Id: Ib428d8cad34dff9b40964ff1a30dcd627c8a9072
Reviewed-on: http://review.couchbase.org/57917
Tested-by: buildbot <80754af91bfb6d1073585b046fe0a474ce868509@couchbase.com>
Reviewed-by: Trond Norbye <60edd2ef23891a753f231b0c6f161dc634079a93@gmail.com>

daverigby/memcached,daverigby/memcached,daverigby/kv_engine,daverigby/kv_engine,daverigby/kv_engine,owendCB/memcached,daverigby/kv_engine,owendCB/memcached,couchbase/memcached,daverigby/memcached,couchbase/memcached,owendCB/memcached,owendCB/memcached,couchbase/memcached,daverigby/memcached,couchbase/memcached