Add month/day/year to parse

Some fields come with this format timestamp rather than ISO format.

Change-Id: I9e361a97f4ba42da6b0aab0ac4d9ae126a58c255

pyghmi/util/parse.py

@@ -56,4 +56,8 @@ def parse_time(timeval):
         return datetime.strptime(timeval, '%Y-%m-%d')
     except ValueError:
         pass
+    try:
+        return datetime.strptime(timeval, '%m/%d/%Y')
+    except ValueError:
+        pass
     return None