evalmountdata null pointer before use

evalmountdata null pointer before use

volnamep can be used uninitialized. fix that.

Reviewed-on: http://gerrit.openafs.org/3777
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit bf72dbf3d5550857a8d41c910baaa722690c1eee)

Change-Id: I0d08aeed130882aeda12c0181d5b738d4c889491
Reviewed-on: http://gerrit.openafs.org/3919
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>