test: disable pipefail again in monitor_check_rr()

test: disable pipefail again in monitor_check_rr()

Partially reverts d6b379370485b9651f86b628ce980de719299eb4.

On Ubuntu 26.04 devel, TEST-75-RESOLVED often fails at this stage,
despite the matching query apparently being found:

 + monitor_check_rr '2025-12-18 16:02:54' 'follow10.so.close.signed.test IN CNAME follow11.yet.so.far.signed.test'
  + set +x
  Dec 18 16:02:54 ns1.unsigned.test resolvectl[552]: ← A: follow10.so.close.signed.test IN CNAME follow11.yet.so.far.signed.test
 + monitor_check_rr '2025-12-18 16:02:54' 'follow11.yet.so.far.signed.test IN CNAME follow12.getting.hot.signed.test'
  + set +x
  Dec 18 16:02:54 ns1.unsigned.test resolvectl[552]: ← A: follow11.yet.so.far.signed.test IN CNAME follow12.getting.hot.signed.test
 + monitor_check_rr '2025-12-18 16:02:54' 'follow12.getting.hot.signed.test IN CNAME follow13.almost.final.signed.test'
  + set +x
  Dec 18 16:02:54 ns1.unsigned.test resolvectl[552]: ← A: follow12.getting.hot.signed.test IN CNAME follow13.almost.final.signed.test
 + monitor_check_rr '2025-12-18 16:02:54' 'follow13.almost.final.signed.test IN CNAME follow14.final.signed.test'
  + set +x
  Dec 18 16:02:54 ns1.unsigned.test resolvectl[552]: ← A: follow13.almost.final.signed.test IN CNAME follow14.final.signed.test

Unsetting pipefail, as was done before d6b3793704, appears to fix the
problem.