Avoid check of service type in process_service::exec_succeeded

The only subclass is bgproc_service, and we can just override the
function - so do that instead.

src/includes/proc-service.h

@@ -834,6 +834,7 @@ class process_service : public base_process_service
 class bgproc_service : public process_service
 {
     virtual void handle_exit_status() noexcept override;
+    virtual void exec_succeeded() noexcept override;
     virtual void exec_failed(run_proc_err errcode) noexcept override;
 
     enum class pid_result_t {

src/proc-service.cc

@@ -44,10 +44,6 @@ std::vector<const char *> separate_args(ha_string &s,
 
 void process_service::exec_succeeded() noexcept
 {
-    if (get_type() != service_type_t::PROCESS) {
-        return;
-    }
-
     tracking_child = true;
 
     // This could be a smooth recovery (state already STARTED). No need to do anything here in
@@ -83,6 +79,12 @@ void process_service::exec_succeeded() noexcept
     }
 }
 
+void bgproc_service::exec_succeeded() noexcept
+{
+    // For bgproc service, unlike regular process service, successful execution doesn't mean much;
+    // the process has to terminate (after forking) before we consider it started.
+}
+
 void scripted_service::exec_succeeded() noexcept
 {
     // For a scripted service, this means nothing other than that the start/stop