Add log_only to debug messages (ansible#25545)

Fixes ansible#25544
When `debug` is enabled the debug messages triggered
from `bin/ansible-connection` should be logged only to file
and not on stdout.

bin/ansible-connection

@@ -290,7 +290,7 @@ def main():
         sys.stderr.write(traceback.format_exc())
         sys.exit("FAIL: %s" % e)
 
-    ssh = connection_loader.get('ssh', class_only=True)
+    ssh = connection_loader.get('ssh', class_only=True, log_only=True)
     cp = ssh._create_control_path(pc.remote_addr, pc.connection, pc.remote_user)
 
     # create the persistent connection dir if need be and create the paths

lib/ansible/plugins/__init__.py

@@ -343,6 +343,7 @@ def get(self, name, *args, **kwargs):
 
         found_in_cache = True
         class_only = kwargs.pop('class_only', False)
+        log_only = kwargs.pop('log_only', False)
         if name in self.aliases:
             name = self.aliases[name]
         path = self.find_plugin(name)
@@ -367,7 +368,7 @@ def get(self, name, *args, **kwargs):
                 return None
 
         self._display_plugin_load(self.class_name, name, self._searched_paths, path,
-                                  found_in_cache=found_in_cache, class_only=class_only)
+                                  found_in_cache=found_in_cache, class_only=class_only, log_only=log_only)
         if not class_only:
             try:
                 obj = obj(*args, **kwargs)
@@ -383,7 +384,7 @@ def get(self, name, *args, **kwargs):
         setattr(obj, '_load_name', name)
         return obj
 
-    def _display_plugin_load(self, class_name, name, searched_paths, path, found_in_cache=None, class_only=None):
+    def _display_plugin_load(self, class_name, name, searched_paths, path, found_in_cache=None, class_only=None, log_only=False):
         msg = 'Loading %s \'%s\' from %s' % (class_name, os.path.basename(name), path)
 
         if len(searched_paths) > 1:
@@ -392,7 +393,7 @@ def _display_plugin_load(self, class_name, name, searched_paths, path, found_in_
         if found_in_cache or class_only:
             msg = '%s (found_in_cache=%s, class_only=%s)' % (msg, found_in_cache, class_only)
 
-        display.debug(msg)
+        display.debug(msg, log_only)
 
     def all(self, *args, **kwargs):
         ''' instantiates all plugins with the same arguments '''

lib/ansible/utils/display.py

@@ -174,9 +174,9 @@ def vvvvv(self, msg, host=None):
     def vvvvvv(self, msg, host=None):
         return self.verbose(msg, host=host, caplevel=5)
 
-    def debug(self, msg):
+    def debug(self, msg, log_only=False):
         if C.DEFAULT_DEBUG:
-            self.display("%6d %0.5f: %s" % (os.getpid(), time.time(), msg), color=C.COLOR_DEBUG)
+            self.display("%6d %0.5f: %s" % (os.getpid(), time.time(), msg), color=C.COLOR_DEBUG, log_only=log_only)
 
     def verbose(self, msg, host=None, caplevel=2):
         if self.verbosity > caplevel: