[lit, lldbsuite] Add a bug reference to the failing TestLinuxCore and fix an...

[lit, lldbsuite] Add a bug reference to the failing TestLinuxCore and fix an undefined property in dotest.py

Summary:
1) In TestLinuxCore rather than skipping the tests on Windows, mark them as expected failures and add a bug reference
2) In dotest.py replace the undefined property in the exceptions with the actual property causing the exception

Reviewers: asmith, labath, zturner

Reviewed By: labath, zturner

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D46590

llvm-svn: 331886