Add --verbose flag as valid option for logging

We recently updated how logging was handled and kept -v for verbose mode
but didn't also keep --verbose. The welcome message script supported
--verbose previously so add it back in for compatibility.

Change-Id: I1a5ee6bd860b9953ed0d56b215d930303654f388
diff --git a/jeepyb/log.py b/jeepyb/log.py
index dbd6c65..86e3d39 100644
--- a/jeepyb/log.py
+++ b/jeepyb/log.py
@@ -18,7 +18,7 @@
 
 def setup_logging_arguments(parser):
     """Sets up logging arguments, adds -d, -l and -v to the given parser."""
-    parser.add_argument('-v', dest='verbose', action='store_true',
+    parser.add_argument('-v', '--verbose', dest='verbose', action='store_true',
                         help='verbose output')
     parser.add_argument('-d', dest='debug', action='store_true',
                         help='debug output')