Converted getopt use to px4_getopt

In the posix and qurt builds, getopt is not thread safe so px4_getopt
should be used instead.

Signed-off-by: Mark Charlebois <charlebm@gmail.com>

src/platforms/posix/px4_layer/px4_posix_tasks.cpp

@@ -98,6 +98,7 @@ void
 px4_systemreset(bool to_bootloader)
 {
 	PX4_WARN("Called px4_system_reset");
+	exit(0);
 }
 
 px4_task_t px4_task_spawn_cmd(const char *name, int scheduler, int priority, int stack_size, px4_main_t entry, char * const argv[])