Refactor ipautil.run

The ipautil.run function now returns an object with returncode and
output are accessible as attributes.

The stdout and stderr of all commands are logged (unless skip_output is given).

The stdout/stderr contents must be explicitly requested with a keyword
argument, otherwise they are None.
This is because in Python 3, the output needs to be decoded, and that can
fail if it's not decodable (human-readable) text.

The raw (bytes) output is always available from the result object,
as is "leniently" decoded output suitable for logging.

All calls are changed to reflect this.

A use of Popen in cainstance is changed to ipautil.run.

Reviewed-By: Jan Cholasta <jcholast@redhat.com>

ipatests/test_xmlrpc/test_host_plugin.py

@@ -552,7 +552,7 @@ class TestHostFalsePwdChange(XMLRPC_test):
         ]
 
         try:
-            out, err, rc = ipautil.run(new_args)
+            ipautil.run(new_args)
         except ipautil.CalledProcessError as e:
             # join operation may fail on 'adding key into keytab', but
             # the keytab is not necessary for further tests