Sandbox: Remove multiple stages

While interesitng in theory, there is nothing to be gained here,
because we don't really have user input at those early stages.

As we are also not a privileged process, those early stage
sandboxes in the end are not worth it, since they increase
complexity while there is no benefit in practise.

So, reduce those 3 stages to a single one (enable()), which we
activate after CLI server has launched.

sandbox/sandbox-openbsd.h

@@ -6,10 +6,6 @@ class SandboxOpenBSD : public Sandbox
 {
   public:
 	bool supported() override;
-	bool enableForInit() override;
-	bool enableForWorker() override;
-
-  private:
-	bool seccomp_blacklist(std::vector<int> syscalls);
+	bool enable(std::vector<std::string> fsPaths) override;
 };
 #endif