[Reviewer: Mike] Fix IPv6 when using transports from bono's connection pool to sprout

Mike,

Please can you review this fix to IPv6 support?  When using a pre-selected transport, we need to fill in the `tdata->dest_info` structure to ensure that PJSIP doesn't do its own DNS resolution (which will fail, because it only seems to support IPv4).

I've live-tested and run UTs successfully.  I'm aware your DNS NAPTR/SRV fixes might supersede this - just reject the pull request if merging this will just unnecessarily complicate your merge.

Cheers,

Matt