Fix RobotDrive constructor (4 SpeedControllers).

Previously this was not initializing maxOutput.

Fixes artf4699.

Patch provided by: rossbach.ron@gmail.com

Change-Id: I8de5e4a508412d3ca51c58ea87e490916c3bd67c

wpilibj/wpilibJavaDevices/src/main/java/edu/wpi/first/wpilibj/RobotDrive.java

@@ -175,6 +175,7 @@ public class RobotDrive implements MotorSafety {
     m_frontRightMotor = frontRightMotor;
     m_rearRightMotor = rearRightMotor;
     m_sensitivity = kDefaultSensitivity;
+    m_maxOutput = kDefaultMaxOutput;
     m_allocatedSpeedControllers = false;
     setupMotorSafety();
     drive(0, 0);