Various cleanup to run_command

* Rename fail_on_rc_non_zero to check_rc, much more succinct.
* Simplify method defintion
* Fix command module and drop shell=shell option; whether to use
  shell is determined by if args is a list.

lib/ansible/module_common.py

@@ -677,40 +677,34 @@ class AnsibleModule(object):
                 self.set_context_if_different(src, context, False)
         os.rename(src, dest)
 
-    def run_command(self, args, **kwargs):
+    def run_command(self, args, check_rc=False, close_fds=False, executable=None):
         '''
         Execute a command, returns rc, stdout, and stderr.
         args is the command to run
         If args is a list, the command will be run with shell=False.
         Otherwise, the command will be run with shell=True when args is a string.
-        kwargs is a dict of keyword arguments:
-        - fail_on_rc_non_zero (boolean) Whether to call fail_json in case of
-                                        non zero RC.  Default is False.
+        Other arguments:
+        - check_rc (boolean)  Whether to call fail_json in case of
+                              non zero RC.  Default is False.
         - close_fds (boolean) See documentation for subprocess.Popen().
                               Default is False.
         - executable (string) See documentation for subprocess.Popen().
                               Default is None.
         '''
         if isinstance(args, list):
-            kwargs['shell'] = False
+            shell = False
         elif isinstance(args, basestring):
-            kwargs['shell'] = True
+            shell = True
         else:
             msg = "Argument 'args' to run_command must be list or string"
             self.fail_json(rc=257, cmd=args, msg=msg)
-        if 'fail_on_rc_non_zero' not in kwargs:
-            kwargs['fail_on_rc_non_zero'] = False
-        if 'close_fds' not in kwargs:
-            kwargs['close_fds'] = False
-        if 'executable' not in kwargs:
-            kwargs['executable'] = None
         rc = 0
         msg = None
         try:
             cmd = subprocess.Popen(args,
-                                   executable=kwargs['executable'],
-                                   shell=kwargs['shell'],
-                                   close_fds=kwargs['close_fds'],
+                                   executable=executable,
+                                   shell=shell,
+                                   close_fds=close_fds,
                                    stdout=subprocess.PIPE, stderr=subprocess.PIPE)
             out, err = cmd.communicate()
             rc = cmd.returncode
@@ -718,7 +712,7 @@ class AnsibleModule(object):
             self.fail_json(rc=e.errno, msg=str(e), cmd=args)
         except:
             self.fail_json(rc=257, msg=traceback.format_exc(), cmd=args)
-        if rc != 0 and kwargs['fail_on_rc_non_zero']:
+        if rc != 0 and check_rc:
             msg = err.rstrip()
             self.fail_json(cmd=args, rc=rc, stdout=out, stderr=err, msg=msg)
         return (rc, out, err)