Don't vary debug info for lldb-server tests

Summary:
Debug info is used only by the client and lldb-server tests do not even have the client component
running, as they communicate with the server directly. Therefore, running the tests for each
debug info type is unnecessarry.

This adds general ability to mark a test class as not dependent on debug info, and marks all
lldb-server tests as such.

Reviewers: tberghammer, tfiala

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D18598

llvm-svn: 265017