Reduce code duplication in ProcessGDBRemote

Summary:
SetThreadStopInfo was checking for a breakpoint at the current PC several times. This merges the
identical code into a separate function. I've left one breakpoint check alone, as it was doing
more complicated stuff, and it did not see a way to merge that without making the interface
complicated. NFC.

Reviewers: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D18819

llvm-svn: 265560