python3: remove usage of 'long'

long is replaced by int in python 3:
https://docs.python.org/3.3/whatsnew/3.0.html#integers
https://www.python.org/dev/peps/pep-0237/

We shouldn't use it anymore.

Change-Id: I93d10be011dca0f0bfc506e752abd59510ac65da

paunch/builder/compose1.py

@@ -210,7 +210,7 @@ class ComposeV1Builder(object):
         self.string_arg(cconfig, cmd, 'stop_signal', '--stop-signal')
 
         def duration(a):
-            if isinstance(a, (int, long, float)):
+            if isinstance(a, (int, float)):
                 return a
 
             # match groups of the format 5h34m56s