Update for c/image's update of github.com/gobuffalo/pop

> go get github.com/containers/image/v5@main
> go mod tidy -go=1.16 && go mod tidy -go=1.17
> make vendor

The (go mod tidy) pair is necessary to keep c/image CI working.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

vendor/google.golang.org/grpc/internal/balancer/gracefulswitch/gracefulswitch.go

@@ -193,6 +193,8 @@ func (gsb *Balancer) ExitIdle() {
 		ei.ExitIdle()
 		return
 	}
+	gsb.mu.Lock()
+	defer gsb.mu.Unlock()
 	for sc := range balToUpdate.subconns {
 		sc.Connect()
 	}