viced: Force valid host enumeration flags

viced: Force valid host enumeration flags

Make sure that the callback functions for h_Enumerate and
h_Enumerate_r give us back valid flags values by aborting if they
return an invalid value.

Reviewed-on: http://gerrit.openafs.org/4528
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Derrick Brashear <shadow@dementia.org>
(cherry picked from commit 484b5b4cf4f88a9ddd04cdbe870d9c2959ef266c)

Change-Id: Ia1b7537d7988203bd8c0bbc619c04f5b3f9387a1
Reviewed-on: http://gerrit.openafs.org/4532
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>