integration: set custom flags for dockerd worker

[crazy-max]

Setting bip and default address pool might not be necessary when testing locally but is useful when running on GitHub Runners to avoid overlapping with others on this address space: https://github.com/moby/moby/blob/3ba527d82af53cf752aa6ec39daac14626c41b0f/libnetwork/ipamutils/utils.go#L18-L20

Needs follow-up on moby to set the right env in: https://github.com/moby/moby/blob/3ba527d82af53cf752aa6ec39daac14626c41b0f/.github/workflows/buildkit.yml#L105-L110

Signed-off-by: CrazyMax crazy-max@users.noreply.github.com

[crazy-max]

While testing this change, found out we have TestIntegration/TestSecretMounts/worker=dockerd that fails with latest changes from master: https://github.com/crazy-max/buildkit/actions/runs/4135974815/jobs/7149222126#step:8:2620

=== CONT  TestIntegration/TestSecretMounts/worker=dockerd
    client_test.go:1153: 
        	Error Trace:	/src/client/client_test.go:1153
        	            				/src/client/run.go:88
        	            				/src/client/run.go:197
        	Error:      	Received unexpected error:
        	            	process "test ! -f /run/secrets/mysecret2" did not complete successfully: exit code: 1
        	            	github.com/moby/buildkit/util/stack.Enable
        	            		/src/util/stack/stack.go:77
        	            	github.com/moby/buildkit/util/grpcerrors.FromGRPC
        	            		/src/util/grpcerrors/grpcerrors.go:197
        	            	github.com/moby/buildkit/util/grpcerrors.UnaryClientInterceptor
        	            		/src/util/grpcerrors/intercept.go:41
        	            	google.golang.org/grpc.(*ClientConn).Invoke
        	            		/src/vendor/google.golang.org/grpc/call.go:35
        	            	github.com/moby/buildkit/api/services/control.(*controlClient).Solve
        	            		/src/api/services/control/control.pb.go:2208
        	            	github.com/moby/buildkit/client.(*Client).solve.func2
        	            		/src/client/solve.go:258
        	            	golang.org/x/sync/errgroup.(*Group).Go.func1
        	            		/src/vendor/golang.org/x/sync/errgroup/errgroup.go:75
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1594
        	            	failed to solve
        	            	github.com/moby/buildkit/client.(*Client).solve.func2
        	            		/src/client/solve.go:273
        	            	golang.org/x/sync/errgroup.(*Group).Go.func1
        	            		/src/vendor/golang.org/x/sync/errgroup/errgroup.go:75
        	            	runtime.goexit
        	            		/usr/local/go/src/runtime/asm_amd64.s:1594
        	Test:       	TestIntegration/TestSecretMounts/worker=dockerd
    sandbox.go:264: stdout: /usr/bin/dockerd
    sandbox.go:267: tmpfs on /run/secrets/mysecret type tmpfs (ro,nosuid,nodev,noexec,relatime,inode64)
    sandbox.go:264: stderr: /usr/bin/dockerd
    sandbox.go:267: > startCmd 2023-02-09 16:06:55.229863501 +0000 UTC m=+249.307224537 /usr/bin/dockerd --data-root /tmp/integration2604706285/dyoeomnwwkfrr/root --exec-root /tmp/dxr/dyoeomnwwkfrr --pidfile /tmp/integration2604706285/dyoeomnwwkfrr/docker.pid --containerd-namespace dyoeomnwwkfrr --containerd-plugins-namespace dyoeomnwwkfrrp --host unix:///tmp/docker-integration/dyoeomnwwkfrr.sock --config-file /tmp/integration2604706285/daemon.json --userland-proxy=false --debug --bip=10.66.66.1/24 --default-address-pool=base=10.66.66.0/16,size=24
    sandbox.go:267: time="2023-02-09T16:06:55.279321453Z" level=info msg="Starting up"

@tonistiigi I wonder if #3561 needs changes on moby too? (maybe not yet vendored)