OPENAFS-SA-2018-002 butc: prevent TC_DumpStatus, TC_ScanStatus information leaks

OPENAFS-SA-2018-002 butc: prevent TC_DumpStatus, TC_ScanStatus information leaks

TC_ScanStatus (backup status) and TC_GetStatus (internal backup status
watcher) do not initialize their output buffers.  They leak memory
contents over the wire:

struct tciStatusS
- up to 64 bytes in member taskName (TC_MAXNAMELEN 64)
- up to 64 bytes in member volumeName  "

Initialize the buffers.

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

(cherry picked from commit be0142707ca54f3de99c4886530e7ac9f48dd61c)

Change-Id: I7a97ad1dbab004938085b401929d4925d80ff3b2