reduce log level for io_uring_submit -> -EBUSY message and fix TIME_NS

TIME_NS was never expanded because emper-config.h was not included
in Common.hpp.

The log_level is reduced from Info to Debug because the IoContext reqs_in_uring
has only in debug builds a meaningful value.
And the fact that there where a full CQ during io_uring_submit is captured in the stats
anyway.

Don't record a full CQ before dying in the completer.