vlserver: Tidy up request counting

vlserver: Tidy up request counting

Tidy up the counting of requests and aborts in the vlserver. Don't
hide a variable allocation within a macro, convert macros to inline
functions, and make it possible to not count particular operations
by passing in an opcode of 0.

Reviewed-on: http://gerrit.openafs.org/4769
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit a14e791541bf19c6c377e68bc2f978fba34f94b1)

Change-Id: I1dcea218fbd3097511a93c9a825d6e76e9c8cf59
Reviewed-on: https://gerrit.openafs.org/12085
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>