ans4 server failed to shut down in upforwd test

Job #3640428 failed for f60dd556:

2023-09-06 05:26:40 INFO:upforwd     I:upforwd_tmp_1y_2pk5t:ans4 didn't die when sent a SIGTERM
2023-09-06 05:26:40 ERROR:upforwd Failed to stop servers
2023-09-06 05:26:40 INFO:upforwd     I:upforwd_tmp_1y_2pk5t:Core dump(s) found: /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908 
2023-09-06 05:26:40 INFO:upforwd     D:upforwd_tmp_1y_2pk5t:backtrace from /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908:
2023-09-06 05:26:40 INFO:upforwd     D:upforwd_tmp_1y_2pk5t:--------------------------------------------------------------------------------
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:Core was generated by `/usr/bin/perl ans.pl'.
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:Program terminated with signal SIGABRT, Aborted.
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#0  0x00007f85c2db40d4 in __GI___select (nfds=8, readfds=0x5560c664e9e0, writefds=0x0, exceptfds=0x0, timeout=0x0) at ../sysdeps/unix/sysv/linux/select.c:69
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#0  0x00007f85c2db40d4 in __GI___select (nfds=8, readfds=0x5560c664e9e0, writefds=0x0, exceptfds=0x0, timeout=0x0) at ../sysdeps/unix/sysv/linux/select.c:69
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#1  0x00005560c4591ec7 in Perl_pp_sselect ()
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#2  0x00005560c4536c06 in Perl_runops_standard ()
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#3  0x00005560c4497881 in perl_run ()
2023-09-06 05:26:49 INFO:upforwd     D:/builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t:#4  0x00005560c4469482 in main ()
2023-09-06 05:26:49 INFO:upforwd     D:upforwd_tmp_1y_2pk5t:--------------------------------------------------------------------------------
2023-09-06 05:26:49 INFO:upforwd     D:upforwd_tmp_1y_2pk5t:full backtrace from /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908 saved in /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908-backtrace.txt
2023-09-06 05:26:49 INFO:upforwd     D:upforwd_tmp_1y_2pk5t:core dump /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908 archived as /builds/isc-projects/bind9/bin/tests/system/upforwd_tmp_1y_2pk5t/ans4/core.75908.gz
2023-09-06 05:26:49 ERROR:upforwd Found core dumps or sanitizer reports