volser: Catch EOFs when reading dumps

volser: Catch EOFs when reading dumps

When reading a standard tag, make sure and catch an EOF error
from iod_getc. Otherwise we'll end up trying to parse 0xFF as a
tag length.

Caught by coverity (#985603)

Change-Id: Iae0b1bf71ed495b4f454975a1bfe3aef8fca3e9e
Reviewed-on: http://gerrit.openafs.org/9275
Reviewed-by: Derrick Brashear <shadow@your-file-system.com>
Reviewed-by: Chas Williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>
Tested-by: BuildBot <buildbot@rampaginggeek.com>