Revert r159528 which taught lit's builtin shell test runner about the

Revert r159528 which taught lit's builtin shell test runner about the
'|&' bash syntax. We have lots of users with a bash on their system
which doesn't support this syntax, and as bash is still significantly
faster, we should support them.

The test suite has already been updated to cope with this.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159580 91177308-0d34-0410-b5e6-96231b3b80d8