MB-25464: Do not exit cbstats if stats_perform fails

Exiting early will prevent cbstats collecting stats from other buckets
when running with `-a`.

Change-Id: I36641b06c5c22ea0add46b3bbe91332ec0fc498a
Reviewed-on: http://review.couchbase.org/81627
Well-Formed: Build Bot <[email protected]>
Reviewed-by: James Harrison <[email protected]>
Tested-by: Build Bot <[email protected]>

Author: daverigby

management/cbstats

@@ -66,7 +66,6 @@ def stats_perform(mc, cmd=''):
     except Exception, e:
         print "Stats '%s' are not available from the requested engine. (%s)"\
                 % (cmd, e)
-        sys.exit(1)
 
 def stats_formatter(stats, prefix=" ", cmp=None):
     if stats: