Support random destinations/multiple tests in dnschk and httpurl.

This adds two parameters to the dnschk and httpurl utilities that
can be used for network testing:

--randomname: connects to a random one-time DNS name.
--attempts: repeats the requested operation N times.

Also reformat the code per clang-format's suggestions.

Test: manual
Change-Id: Iab9966c489f8fa692eb9f7974ba25281ddf80b06
4 files changed