OPENAFS-SA-2018-002 kaserver: prevent KAM_ListEntry information leak

OPENAFS-SA-2018-002 kaserver: prevent KAM_ListEntry information leak

KAM_ListEntry (kas list) does not initialize its output correctly.  It
leaks kaserver memory contents over the wire:

struct kaindex
- up to 64 bytes for member name
- up to 64 bytes for member instance

Initialize the buffer.

[kaduk@mit.edu: move initialization to top of server routine]

(cherry picked from commit b604ee7add7be416bf20973422a041e913d20761)

Change-Id: Ic40bb2d5af409399c11a378340ba92174e26112f