Fix up this test case.

The lldbutil.run_break_set_by_file_and_line has already checked that the number of 
locations was 1, so don't check it again.  And certainly don't check it again by 
grubbing in break list output.

Also, we know the Thread's IsStopped state is wrong, and have a test for that, so 
don't keep testing it in other files where that isn't the primary thing we're testing.

I removed the xfail for Darwin.  If this also passes on other systems, we can remove
the xfails from them as we find that out.

llvm-svn: 282993