clear connections if a cached producer is closed
clear connections if a cached producer is closed

refs FOO-2190

TEST PLAN:
  1) run pulsar AUA log compation
  2) reboot pulsar brokers
  3) we don't get big error spikes

Change-Id: I81404ab4b67c426c3e6e796ebbc2c0925939383f
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/269718
Reviewed-by: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>
Product-Review: Charley Kline <05950d7e90ba5e3da323378368c22b3ffaaf6647@instructure.com>
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
QA-Review: Ethan Vizitei <73eeb0b2f65d05a906adf3b21ee1f9f5a2aa3c1c@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms