drx-test fails occasionally on ARM due to missing nudge

This happened once, on ARM. Not easy to repro:

```
80/90 Testing: code_api|client.drx-test
80/90 Test: code_api|client.drx-test
Command: "/home/derek/dr/git/build_local/bin32/drrun" "-s" "60" "-quiet" "-debug" "-killpg" "-stderr_mask" "0xC" "-dumpcore_mask" "0" "-code_api" "-c" "/home/derek/dr/git/build_local/suite/tests/bin/libclient.drx-test.dll.so" "--" "/home/derek/dr/git/build_local/suite/tests/bin/client.drx-test"
Directory: /home/derek/dr/git/build_local/suite/tests
"code_api|client.drx-test" start time: Jul 06 16:09 EDT
Output:
----------------------------------------------------------
creating child
terminating child by sending SIGKILL
event_exit
child exit code = 132
event_exit

Test time = 5.10 sec
----------------------------------------------------------
Test Fail Reason:
Required regular expression not found.Regex=[^creating child
terminating child by sending SIGKILL
event_nudge exit code 2304
event_exit
child exit code = 9
event_exit
$
]
```