test: fix threading for FaultInjector death tests

test: fix threading for FaultInjector death tests

addresses test timeout and warning message:

[WARNING] /home/jenkins-build/build/workspace/ceph-pull-requests/src/googletest/googletest/src/gtest-death-test.cc:1121:: Death tests use fork(), which is unsafe particularly in a threaded context. For this test, Google Test detected 3 threads. See https://github.com/google/googletest/blob/master/googletest/docs/advanced.md#death-tests-and-threads for more explanation and suggested solutions, especially if this is the last message you see before your test times out.

Signed-off-by: Casey Bodley <cbodley@redhat.com>