OpenBSD: Fix parameters in call to afs_close()

OpenBSD: Fix parameters in call to afs_close()

OpenBSD passes an extra parameter in a call to afs_close()
in its OS-specific code. It went undetected in the past
but now causes compile headaches because of more accurate
prototypes in the header file. This patch removes the
offending extra parameter (which never actually caused any
problems because it was the last one in the parameter list).

Change-Id: I6bde0c6c98867c47a574fa5e3e01ec560deb17b0
Reviewed-on: http://gerrit.openafs.org/3685
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>