Stop logfileconfig/ns1 server with TERM signal

stop.pl tries to stop ns1 via rndc but fails to find rndc.conf because the logfileconfig test code is unexpectedly executed from the logfileconfig/ns1/ directory. Instead of stopping ns1 with rndc, it waits for 30 seconds and then terminates ns1 with the TERM signal. Stop ns1 with the TERM signal directly.

I:logfileconfig:testing default logfile using named -L file (9)
rndc: ../common/rndc.conf does not exist

See https://gitlab.isc.org/isc-projects/bind9/-/jobs/3178919#L389.