remote: properly initialize objects in ACL helpers

remote: properly initialize objects in ACL helpers

Commit 2ecdf259299813c2c674377e22a0acbce5ccbbb2 was intended to
implement two things: reduce stack usage inside ACL helpers and
minimally initialize virDomainDef object to avoid passing garbage
inside validation framework. Though original commit has not
touched other ACL helpers.

This patch adds proper clauses to
    remoteRelayNetworkEventCheckACL
    remoteRelayStoragePoolEventCheckACL
    remoteRelayNodeDeviceEventCheckACL
    remoteRelaySecretEventCheckACL

Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>