Tests: rewrite 'opt ... %s' to 'opt ... < %s' so that opt does not emit a ModuleID

This is done to avoid odd test failures, like the one fixed in r171243.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173163 91177308-0d34-0410-b5e6-96231b3b80d8