afsmonitor: Fix multiple NUM_CM_STAT_ENTRIES overflows

If an array is n elements long, accessing element array[n] is an
overflow. Fix various places where we apply loop bounds incorrectly
using the NUM_CM_STAT_ENTRIES constant.

Caught by coverity (#985571, #985573)

Change-Id: I24a53e8044d3d5d39d070909400329a82f22b6b9
Reviewed-on: http://gerrit.openafs.org/9316
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>