Fix a bug in the userspace AVC that broke per-domain permissive mode.

Failure to copy the entire av_decision structure, including the
flags field, would prevent preservation of the SELINUX_AVD_FLAGS_PERMISSIVE
flag and thus cause per-domain permissive to not be honored for userspace
permission checks.

Also ensure that we clear the entire structure.

Change-Id: I92fcb2522d05094a9583b0035bbe1f94cb289ecd
Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>