Fix TestBreakpointInGlobalConstructor for Windows

Summary:
This test was failing on Windows because it expected the breakpoint in the
dynamic library to be resolved before the process is launched.  Since the DLL
isn't loaded until the process is launched this didn't work.

The fix creates a special value (-2) for num_expected_locations that ignores
the actual number of breakpoint locations found.

Reviewers: jasonmolenda

Subscribers: sanjoy, lldb-commits

Differential Revision: https://reviews.llvm.org/D43419

llvm-svn: 325704