Adjust io-level logging in gerrit/git drivers

Currently the logging for polling is verbose.  Adjust it as follows:

* In the git driver, don't list every ref we see, just log the count
  so we know it's working.
* In the gerrit driver, move logging of some HTTP traffic to the
  "io" logger.
* In the default logging configuration for the server, if the '-d'
  option is given, do not include "io" logging.  The only way to
  get this extremely verbose data is now with a custom logging
  config.

Change-Id: If0d5877f65296ee2a9f7f0298f8bc6664e6c2a4c

zuul/ansible/logconfig.py

@@ -90,6 +90,10 @@ _DEFAULT_SERVER_LOGGING_CONFIG = {
             'handlers': ['console'],
             'level': 'INFO',
         },
+        'zuul.GerritConnection.io': {
+            'handlers': ['console'],
+            'level': 'WARN',
+        },
         'sqlalchemy.engine': {
             'handlers': ['console'],
             'level': 'WARN',

zuul/driver/gerrit/gerritconnection.py

@@ -612,7 +612,7 @@ class GerritConnection(BaseConnection):
             verify=self.verify_ssl,
             auth=self.auth, timeout=TIMEOUT,
             headers={'User-Agent': self.user_agent})
-        self.log.debug('Received: %s %s' % (r.status_code, r.text,))
+        self.iolog.debug('Received: %s %s' % (r.status_code, r.text,))
         if r.status_code != 200:
             raise Exception("Received response %s" % (r.status_code,))
         ret = None
@@ -636,7 +636,7 @@ class GerritConnection(BaseConnection):
             auth=self.auth, timeout=TIMEOUT,
             headers={'Content-Type': 'application/json;charset=UTF-8',
                      'User-Agent': self.user_agent})
-        self.log.debug('Received: %s %s' % (r.status_code, r.text,))
+        self.iolog.debug('Received: %s %s' % (r.status_code, r.text,))
         if r.status_code != 200:
             raise Exception("Received response %s" % (r.status_code,))
         ret = None

zuul/driver/git/gitwatcher.py

@@ -116,7 +116,8 @@ class GitWatcher(threading.Thread):
         try:
             for project in self.connection.projects:
                 refs = self.lsRemote(project)
-                self.log.debug("Read refs %s for project %s" % (refs, project))
+                self.log.debug("Read %s refs for project %s",
+                               len(refs), project)
                 if not self.projects_refs.get(project):
                     # State for this project does not exist yet so add it.
                     # No event will be triggered in this loop as