webhook: set securityContext
webhook: set securityContext

To follow the least privilege principle, the conversion and admission webhooks
are run with a non-root user (uid = 2000).

Longhorn 3701

Signed-off-by: Derek Su <7c7ccabf9108ae9b71ea7c9fe9c3cfcdea8fd20d@suse.com>

rancher/longhorn