Use log.info rather than log.err

Sometimes stderr may have output and showing it with ERROR may cause
misinterpretation.

Change-Id: I92b00feeed3bc3c8394f5bf54035b9b588c97c00

plugin_source/deployment_scripts/utils.py

@@ -57,7 +57,7 @@ def execute(*cmd, **kwargs):
     if out:
         logging.debug(out)
     if err:
-        logging.error(err)
+        logging.info(err)
 
     if proc.returncode is not None and proc.returncode != 0:
         raise ExecutionError(err)