ptuser/hpr: Don't check for a KeyFile

ptuser/hpr: Don't check for a KeyFile

ptuser and viced's hpr were checking for a KeyFile before calling
ClientAuthSecure. If a KeyFile doesn't exist, then they would display
a warning message, and use an rxnull connection.

However, ClientAuthSecure will return a rxnull connection if it can't
find a KeyFile. So, simplify all of this to just use ClientAuthSecure,
which knows better than we do what keys are usable and which aren't.

Change-Id: I14b6170ec49e0ca85bc371d3bdfa04aecf39f150
Reviewed-on: http://gerrit.openafs.org/4100
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>