The monotonic clock is preferred as it is guaranteed to be
continuous and not subject to jumps due to adjustments.
* lib/net/resolv.rb (request): use monotonic clock
* lib/net/http.rb (begin_transport, end_transport): ditto
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@50664 b2dd03c8-39d4-4d8f-98ff-823fe69b080e