[TestDataFormatterUnordered] Use patterns to match unordered_<multi>set elements

Summary: This fixes the test for i386 targets.

Test Plan: dotest.py -C clang --arch i386 TestDataFormatterUnordered

Reviewers: chying, chaoren, clayborg

Reviewed By: clayborg

Subscribers: lldb-commits

Differential Revision: http://reviews.llvm.org/D10078

llvm-svn: 238385