Added debugserver/llgs test for command-line --attach {pid} variant.

Checks that the pid reported by $qProcessInfo matches the pid that was
launched as the attach test subject.

test exe now supports "sleep:{sleep_seconds}" command line argument.


git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@208782 91177308-0d34-0410-b5e6-96231b3b80d8