Drop #1941 workaround

Workaround for issue #1941 (closed) is not needed anymore as the underlying performance issue which manifested on FreeBSD was addressed:

• main stress:authoritative:freebsd12:amd64:

2021-01-18:09:52:49 INFO: Server 'ns2' (authoritative) received 20,010,100 TCP queries
2021-01-18:09:52:49 INFO: About 21,600,000 TCP queries were expected
2021-01-18:09:52:49 INFO: Minimum number of TCP queries required to pass is 19,440,000
2021-01-18:09:52:49 INFO: BIND processed enough TCP queries

• v9_16 stress:authoritative:freebsd12:amd64:

2021-01-19:07:44:36 INFO: Server 'ns2' (authoritative) received 20,672,860 TCP queries
2021-01-19:07:44:36 INFO: About 21,600,000 TCP queries were expected
2021-01-19:07:44:36 INFO: Minimum number of TCP queries required to pass is 19,440,000
2021-01-19:07:44:36 INFO: BIND processed enough TCP queries

• v9_11 stress:authoritative:freebsd12:amd64:

2021-01-18:05:38:05 INFO: Server 'ns2' (authoritative) received 11,490,100 TCP queries
2021-01-18:05:38:05 INFO: About 21,600,000 TCP queries were expected
2021-01-18:05:38:05 INFO: Minimum number of TCP queries required to pass is 19,440,000
2021-01-18:05:38:05 ERROR: BIND did not process enough TCP queries