txlb.ProxyService.getEnabledGroup does not always return an enabled group

This report is for txLoadBalancer-1.1.0

getEnabledGroup determines determines the enabled groups on line 94 with:
groups = [x for x in self.groups.values() if x.isEnabled]

It expects x.isEnabled to evaluate to True only for enabled groups.

However, when txlb.application.director.configuredProxyManagerFactory instantiates txlb.model.ProxyGroup (line 41-42), it passes in groupConf.isEnabled, which is a bound method. When this is evaluated in the list comprehension shown above, it always evaluates to True for all groups.

The fix appears to be to change:
groupConf.isEnabled
to:
groupConf.isEnabled()