TCPSocket: add back support for "*" address

before r301492, we could specify "*:1234" as an address to lldb-server
and it would interpret that as "any". I am not sure that's a good idea,
but we have usages of that in the test suite, and without this the
remote test suite fails.

I'm adding that back, as it does not seem it was an intended side-effect
of that change, but I am open to removing it in the future, after
discussion and test suite fixup.

llvm-svn: 301534