Use run_main_loop_until_done() for process_t tests.

This patch changes the slow process_t tests to use
run_main_loop_until_done() instead of do_main_loop() since
do_main_loop() initializes a lot of subsystem callbacks that we don't
need to run in our tests.

See: https://bugs.torproject.org/28179

src/core/mainloop/mainloop.c

@@ -200,7 +200,6 @@ static int can_complete_circuits = 0;
 #define LAZY_DESCRIPTOR_RETRY_INTERVAL (60)
 
 static int conn_close_if_marked(int i);
-static int run_main_loop_until_done(void);
 static void connection_start_reading_from_linked_conn(connection_t *conn);
 static int connection_should_read_from_linked_conn(connection_t *conn);
 static void conn_read_callback(evutil_socket_t fd, short event, void *_conn);
@@ -2847,10 +2846,6 @@ do_main_loop(void)
     }
   }
 #endif /* defined(HAVE_SYSTEMD_209) */
-
-  main_loop_should_exit = 0;
-  main_loop_exit_value = 0;
-
 #ifdef ENABLE_RESTART_DEBUGGING
   {
     static int first_time = 1;
@@ -2976,10 +2971,14 @@ run_main_loop_once(void)
  *
  * Shadow won't invoke this function, so don't fill it up with things.
  */
-static int
+STATIC int
 run_main_loop_until_done(void)
 {
   int loop_result = 1;
+
+  main_loop_should_exit = 0;
+  main_loop_exit_value = 0;
+
   do {
     loop_result = run_main_loop_once();
   } while (loop_result == 1);

src/core/mainloop/mainloop.h

@@ -100,6 +100,7 @@ extern struct token_bucket_rw_t global_bucket;
 extern struct token_bucket_rw_t global_relayed_bucket;
 
 #ifdef MAINLOOP_PRIVATE
+STATIC int run_main_loop_until_done(void);
 STATIC void close_closeable_connections(void);
 STATIC void initialize_periodic_events(void);
 STATIC void teardown_periodic_events(void);

src/test/test_process_slow.c

@@ -6,6 +6,7 @@
  * \brief Slow test cases for the Process API.
  */
 
+#define MAINLOOP_PRIVATE
 #include "orconfig.h"
 #include "core/or/or.h"
 #include "core/mainloop/mainloop.h"
@@ -168,7 +169,7 @@ run_main_loop(void)
                                                NULL);
 
   /* Run our main loop. */
-  ret = do_main_loop();
+  ret = run_main_loop_until_done();
 
   /* Clean up our main loop timeout timer. */
   tt_int_op(ret, OP_EQ, 0);