reduce debugging from utils.trycmd()

In the case where the command fails, we're returning
the err anyway and the caller can log if required.

In the discard_warnings=True case, then the caller
has explicitly asked to suppress the warnings,
so don't log this noise either.

Fixes bug: 1030609
Change-Id: I075c21aa6508182ae6dd030cf41ec31916559957

nova/utils.py

@@ -223,12 +223,10 @@ def trycmd(*args, **kwargs):
         failed = False
     except exception.ProcessExecutionError, exn:
         out, err = '', str(exn)
-        LOG.debug(err)
         failed = True
 
     if not failed and discard_warnings and err:
         # Handle commands that output to stderr but otherwise succeed
-        LOG.debug(err)
         err = ''
 
     return out, err