Correct strftime callers

Correct strftime callers

Some strftime callers were not using the resultant string
appropriately. Correct them to have the same behavior as when we were
using afs_ctime (which included a trailing newline).

Change-Id: I1d23a6a06460cae3d2a253c9f084c22324fc7542
Reviewed-on: http://gerrit.openafs.org/4437
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Reviewed-by: Simon Wilkinson <sxw@inf.ed.ac.uk>
Tested-by: BuildBot <buildbot@rampaginggeek.com>