vl.c: remove init_clocks call from main

Clocks are initialized in qemu_init_main_loop. They are not needed before it.
Initializing them twice is not only unnecessary but is harmful: it results in
memory leak and potentially can lead to a situation where different parts of
QEMU use different sets of timers.

To avoid it remove init_clocks call from main and add an assertion to
qemu_clock_init that corresponding clock has not been initialized yet.
Signed-off-by: NKirill Batuzov <batuzovk@ispras.ru>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

qemu-timer.c

@@ -126,6 +126,9 @@ static void qemu_clock_init(QEMUClockType type)
 {
     QEMUClock *clock = qemu_clock_ptr(type);
 
+    /* Assert that the clock of type TYPE has not been initialized yet. */
+    assert(main_loop_tlg.tl[type] == NULL);
+
     clock->type = type;
     clock->enabled = true;
     clock->last = INT64_MIN;

vl.c

@@ -3024,7 +3024,6 @@ int main(int argc, char **argv, char **envp)
 
     runstate_init();
 
-    init_clocks();
     rtc_clock = QEMU_CLOCK_HOST;
 
     qemu_init_auxval(envp);