Change TestAbbreviations test to expected failure on Linux.

See http://llvm.org/bugs/show_bug.cgi?id=18816.
Likely the same issue as http://llvm.org/bugs/show_bug.cgi?id=18805.



git-svn-id: https://llvm.org/svn/llvm-project/lldb/trunk@201244 91177308-0d34-0410-b5e6-96231b3b80d8