ArduCopter CLI: Add imu.init before imu.init_accel for "level"

* Depending on when you entered the CLI, the imu might not be
  initialized yet, and init_accel would hang.

ArduCopter/setup.pde

@@ -245,6 +245,7 @@ setup_motors(uint8_t argc, const Menu::arg *argv)
 static int8_t
 setup_accel(uint8_t argc, const Menu::arg *argv)
 {
+  imu.init(IMU::COLD_START, delay, &timer_scheduler);
 	imu.init_accel();
 	print_accel_offsets();
 	report_imu();