avocado.core.output: Add missing attribute for OutputManager

So the vm plugin can correctly determine the logs dir.
Signed-off-by: NLucas Meneghel Rodrigues <lmr@redhat.com>

avocado/core/output.py

@@ -204,6 +204,7 @@ class OutputManager(object):
         :param logfile: Path to file that will receive logging.
         :param loglevel: Level of the logger. Example: :mod:`logging.DEBUG`.
         """
+        self.debuglog = logfile
         self.file_handler = logging.FileHandler(filename=logfile)
         self.file_handler.setLevel(loglevel)