HAL_Linux: run threads a bit more slowly

this was just wasting cycles

libraries/AP_HAL_Linux/Scheduler.cpp

@@ -214,7 +214,7 @@ void *LinuxScheduler::_timer_thread(void)
 {
     _setup_realtime(32768);
     while (true) {
-        _microsleep(1000);
+        _microsleep(5000);
 
         // run registered timers
         _run_timers(true);
@@ -246,7 +246,7 @@ void *LinuxScheduler::_uart_thread(void)
 {
     _setup_realtime(32768);
     while (true) {
-        _microsleep(1000);
+        _microsleep(10000);
 
         // process any pending serial bytes
         ((LinuxUARTDriver *)hal.uartA)->_timer_tick();
@@ -260,7 +260,7 @@ void *LinuxScheduler::_io_thread(void)
 {
     _setup_realtime(32768);
     while (true) {
-        _microsleep(1000);
+        _microsleep(20000);
 
         // process any pending storage writes
         ((LinuxStorage *)hal.storage)->_timer_tick();