[BPF] Remove exit-on-error flag in test (PR27767)

The exit-on-error flag is needed to avoid an assert where
llvm::SelectionDAGISel::LowerArguments doesn't create enough arguments. Fill up
with zeroes to reach the right number of args.

Fixes PR27767.

Differential Revision: http://reviews.llvm.org/D20571

llvm-svn: 270855