Fix unchecked return values

Fix unchecked return values

This change fixes numerous places where the return values of various
system calls and standard library routines are not checked.  In
particular, this fixes occurrances called out when building on Ubuntu
12.10, with gcc 4.7.2 and eglibc 2.15-0ubuntu20.1, when the possible
failure is one we actually do (or should) care about.  This change
does not consider calls where the failure is one we deliberately
choose to ignore.

Change-Id: Id526f5dd7ee48be2604b77a3f00ea1e51b08c21d
Reviewed-on: http://gerrit.openafs.org/9979
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Jeffrey Altman <jaltman@your-file-system.com>