This enables golangci-lint via build tags for integration tests (this
should have been done long ago!), and fixes the linting errors.
Two tests were updated to reduce flakiness:
* apply config: wait for nodes to issue "boot done" sequence event
before proceeding
* recover: kill pods even if they appear after the initial set gets
killed (potential race condition with previous test).
Signed-off-by: Andrey Smirnov <smirnov.andrey@gmail.com>