Run tests: Re-enable signal_dumper on target

I have previously (3 years ago) disabled it during gcstress
investigation to let it propagate to testrunner.py (which
should be sufficient on its own).  However, we have seen
recent runs where that somehow didn't work.

Re-enable the singal_dummper on target again to add the
second level of protection. This will also be necessary
for trade-fed, since it will not run in testrunner.py.

Test: "/art/test.py -r --optimizing --64" with low timeout
Change-Id: Ic03785599d1a8bf90d6f89f1ad650fbc59fcdf6e
diff --git a/test/default_run.py b/test/default_run.py
index c50c22e..f457956 100755
--- a/test/default_run.py
+++ b/test/default_run.py
@@ -290,7 +290,7 @@
   PREBUILD = args.prebuild
   RELOCATE = args.relocate
   SECONDARY_DEX = ""
-  TIME_OUT = "n"  # "n" (disabled), "timeout" (use timeout), "gdb" (use gdb)
+  TIME_OUT = "timeout"  # "n" (disabled), "timeout" (use timeout), "gdb" (use gdb)
   TIMEOUT_DUMPER = "signal_dumper"
   # Values in seconds.
   TIME_OUT_EXTRA = 0
@@ -1060,7 +1060,7 @@
       #       dumping do not lead to a deadlock, we also use the "-k" option to definitely kill the
       #       child.
       # Note: Using "--foreground" to not propagate the signal to children, i.e., the runtime.
-      timeout_prefix = f"timeout --foreground -k 120s {TIME_OUT_VALUE}s {timeout_dumper_cmd} {cmdline}"
+      timeout_prefix = f"timeout --foreground -k 120s {TIME_OUT_VALUE}s {timeout_dumper_cmd}"
 
     ctx.export(
       ASAN_OPTIONS = RUN_TEST_ASAN_OPTIONS,