Micro-optimization: replace s.find(x)!=-1 with x in s

timeit shows a speedup of ~3x on Python 2.7.5 x86_64.
It also makes the code a bit shorter.

lib/ansible/module_utils/known_hosts.py

@@ -98,7 +98,7 @@ def not_in_host_file(self, host):
             host_fh.close()
 
         for line in data.split("\n"):
-            if line is None or line.find(" ") == -1:
+            if line is None or " " not in line:
                 continue
             tokens = line.split()
             if tokens[0].find(HASHED_KEY_MAGIC) == 0: