macos: add anchors to synthetic.conf grep pattern
The grep pattern that checks if /etc/synthetic.conf already has an entry
for afs is intended to check if this file holds a single column entry
named afs. Unfortunately, the current version does not completely
enforce this restriction. To fix this problem, add anchors to the grep
pattern in question.
Change-Id: I15a1fa1c250027b7d3ab67e686cbfbae853251a2
Reviewed-on: https://gerrit.openafs.org/14062
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Reviewed-by: Yadavendra Yadav <yadayada@in.ibm.com>
Reviewed-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>