This seems to be a pretty old bug, older then originally reported (at
least under certain circumstances).
The IP singleton uses a resolve queue so developers can queue hostnames
for resolution in a separate while keeping the main thread unlocked
(address-resolution OS functions are blocking, and could block for a long
time in case of network disruption).
In most places though, the address resolution function was called with
the mutex locked, causing other functions (querying status, queueing
another hostname, ecc) to block until that resolution ended.
This commit ensures that all calls to OS address resolution are done
with the mutex unlocked.
aca5540e13