Validate format strings for CLS_ERR/CLS_LOG

cls_log needed __attribute__((format(printf..)) to allow the compiler
to crosscheck format strings and arguments.  After adding that, there
needed to be a bunch of fixups for %ll, and a few changes for missing
arguments, etc. uncovered by the checking.

Fixes: #3970
Signed-off-by: Dan Mick <dan.mick@inktank.com>