mountstats: division by zero error on new mount when 0==rpcsends

When rpcsends is 0 this is the error seen when mounstats is run on a
NFSv4.2 mount

Fixes: https://bugzilla.linux-nfs.org/show_bug.cgi?id=367
Signed-off-by: Steve Dickson <steved@redhat.com>
diff --git a/tools/mountstats/mountstats.py b/tools/mountstats/mountstats.py
index 23876fc..8e129c8 100755
--- a/tools/mountstats/mountstats.py
+++ b/tools/mountstats/mountstats.py
@@ -482,8 +482,11 @@
             count = stats[1]
             if count != 0:
                 print('%s:' % stats[0])
+                ops_pcnt = 0
+                if sends != 0:
+                    ops_pcnt = (count * 100) / sends
                 print('\t%d ops (%d%%)' % \
-                    (count, ((count * 100) / sends)), end=' ')
+                    (count, ops_pcnt), end=' ')
                 retrans = stats[2] - count
                 if retrans != 0:
                     print('\t%d retrans (%d%%)' % (retrans, ((retrans * 100) / count)), end=' ')