This commit extends SwarmKit secret management with pluggable secret backends support. Updating the work in [swarmkit](docker/swarmkit@eebac27434) for pluggable secret backend and adding the driver parameter to `SecretSpec`. Remaining work: - [ ] CLI support (docker/cli) - [ ] api in [plugin helpers](docker/go-plugins-helpers)) - [ ] Reference plugin - [ ] Documenation (after cli work) Signed-off-by: Liron Levin <liron@twistlock.com> Upstream-commit: 7d45cafd5746e847e58078aa2fbdde57b5f49fa4 Component: engine