[clang-format][tests] Explicitly specify style in some tests

Summary: This fixes broken tests when doing an out-of-source build that picks up a random .clang-format on the file system due to the default "file" style.

Reviewers: djasper, klimek, MyDeveloperDay, krasimir

Reviewed By: MyDeveloperDay

Subscribers: lebedev.ri, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61001

llvm-svn: 365909