libselinux - correct selabel invalid context logging

When selabel_lookup found an invalid context with validation enabled, it
always stated it was 'file_contexts' whether media, x, db or file.
The fix is to store the spec file name in the selabel_lookup_rec on
selabel_open and use this as output for logs. Also a minor fix if key is
NULL to stop seg faults.

Signed-off-by: Richard Haines <richard_c_haines@btinternet.com>
Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Dan Walsh <dwalsh@redhat.com>
7 files changed