Trying to use the FEATURE_CHECK RPC with criu_req->criu_opts set to NULL
makes CRIU segfault. Technically there is no reason to have a valid
criu_req->criu_opt during feature check. The only reason was to set the
image directory for setproctitle(). This removes the segfault and the
unnecessary requirement of setting criu_req->criu_opts.

Another possible solution would have been to return an error if
criu_req->criu_opts is NULL but so far it seems unnecessary to have
criu_req->criu_opts during feature check.
Signed-off-by: Adrian Reber <areber@redhat.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>