Relax IsolateDestAddr rules to handle hostname/ip distinction
The current prop171 branch takes a simplistic view of isolating streams by destination address, and treats any two addresses as equal only if they equal in a case-insensitive string comparison. But if address A has resolved to IP B, then perhaps we don't want to isolate future requests for A and B onto separate circuits.
There may also be other circumstances like this, such as where hostname A and hostname B are both known to resolve to IP C.