Make lock_host_keys a real noop, instead of half-a-noop

Right now, we don't do any locking, but we still scan known_hosts files
twice per connection. That's completely unnecessary, and the proposed
solutions to the locking problem wouldn't need known_hosts scanning
anyway, so this code can go away.

lib/ansible/plugins/connections/ssh.py

@@ -207,73 +207,17 @@ class Connection(ConnectionBase):
         stdin.close()
         return (p.returncode, stdout, stderr)
 
-    def not_in_host_file(self, host):
-        if 'USER' in os.environ:
-            user_host_file = os.path.expandvars("~${USER}/.ssh/known_hosts")
-        else:
-            user_host_file = "~/.ssh/known_hosts"
-        user_host_file = os.path.expanduser(user_host_file)
-
-        host_file_list = []
-        host_file_list.append(user_host_file)
-        host_file_list.append("/etc/ssh/ssh_known_hosts")
-        host_file_list.append("/etc/ssh/ssh_known_hosts2")
-
-        hfiles_not_found = 0
-        for hf in host_file_list:
-            if not os.path.exists(hf):
-                hfiles_not_found += 1
-                continue
-            try:
-                host_fh = open(hf)
-            except IOError as e:
-                hfiles_not_found += 1
-                continue
-            else:
-                data = host_fh.read()
-                host_fh.close()
-
-            for line in data.split("\n"):
-                if line is None or " " not in line:
-                    continue
-                tokens = line.split()
-                if not tokens:
-                    continue
-
-                if isinstance(tokens, list) and tokens: # skip invalid hostlines
-                    if tokens[0].find(self.HASHED_KEY_MAGIC) == 0:
-                        # this is a hashed known host entry
-                        try:
-                            (kn_salt,kn_host) = tokens[0][len(self.HASHED_KEY_MAGIC):].split("|",2)
-                            hash = hmac.new(kn_salt.decode('base64'), digestmod=sha1)
-                            hash.update(host)
-                            if hash.digest() == kn_host.decode('base64'):
-                                return False
-                        except:
-                            # invalid hashed host key, skip it
-                            continue
-                    else:
-                        # standard host file entry
-                        if host in tokens[0]:
-                            return False
-
-        if (hfiles_not_found == len(host_file_list)):
-            self._display.vvv("EXEC previous known host file not found for {0}".format(host))
-        return True
-
     def lock_host_keys(self, lock):
 
-        if C.HOST_KEY_CHECKING and  self.not_in_host_file(self.host):
-            if lock:
-               action = fcntl.LOCK_EX
-            else:
-               action = fcntl.LOCK_UN
+        # lock around the initial SSH connectivity so the user prompt about
+        # whether to add the host to known hosts is not intermingled with
+        # multiprocess output.
+        #
+        # This is a noop for now, pending further investigation. The lock file
+        # should be opened in TaskQueueManager and passed down through the
+        # PlayContext.
 
-            # lock around the initial SSH connectivity so the user prompt about whether to add
-            # the host to known hosts is not intermingled with multiprocess output.
-        # FIXME: move the locations of these lock files, same as init above, these came from runner, probably need to be in task_executor
-        #    fcntl.lockf(self.process_lockfile, action)
-        #    fcntl.lockf(self.output_lockfile, action)
+        pass
 
     def exec_command(self, *args, **kwargs):
         """