thread sanitizer reporting unit test in control agent

https://jenkins.isc.org/job/kea-1.7/job/ut-thread/3/testReport/

CtrlAgentControllerTest.sigintShutdown

Error Message
ca_controller_unittests.cc:255
Value of: elapsed_time.total_milliseconds() < 300
  Actual: false
Expected: true
Stacktrace
ca_controller_unittests.cc:255
Value of: elapsed_time.total_milliseconds() < 300
  Actual: false
Expected: true

failing on freebsd 12 and ubuntu 1910