[log] use THROTTLE_MSG for KLOG_EVERY_N_SECS when necessary

As a follow-up to e8f459284 and 8bc0be58e, this patch updates call sites
of KLOG_EVERY_N_SECS w.r.t. using THROTTLE_MSG to report on the number
of suppressed messages.  The rationale behind this update is to provide
extra information that is useful for troubleshooting, according to my
findings while troubleshooting a few recent issues.

In addition, I added one micro-test for KLOG_EVERY_N_SECS when used
without THROTTLE_MSG and removed useless logging in another test: it
seems the logging was added there just for debugging while implementing
the test.  I also took the liberty of updating corresponding messages
and the logging frequency to be more appropriate.

Otherwise, this patch doesn't contain any functional modifications.

Change-Id: I1ef2952b86b15f15cd8cd806619e5113ad1c758f
Reviewed-on: http://gerrit.cloudera.org:8080/20855
Tested-by: Kudu Jenkins
Reviewed-by: Abhishek Chennaka <achennaka@cloudera.com>
11 files changed