[ops][cinder] warning about os-brick release 4.2.0

This message applies to operators using cinder drivers that use the os-brick nvmeof connector. os-brick release 4.2.0, released on 16 February, contains a refactored nvmeof connector that unfortunately introduced a regression in the connector interface and breaks older drivers that use the nvmeof connector. So if you use such a driver, do not upgrade to 4.2.0. This issue will be resolved before the "official" wallaby os-brick release. You can follow events as they unfold on Bug #1916264: https://bugs.launchpad.net/os-brick/+bug/1916264