Fix mismatch between RigidBody(2D) and Body(2D)SW can_sleep defaults.

- Set Body2DSW can_sleep default to true.

- Set Body2D can_sleep default to true.

(cherry picked from commit 42a9ae7a82)

servers/physics/body_sw.cpp

@@ -791,7 +791,7 @@ BodySW::BodySW() :
 
 	still_time = 0;
 	continuous_cd = false;
-	can_sleep = false;
+	can_sleep = true;
 	fi_callback = NULL;
 }
 

servers/physics_2d/body_2d_sw.cpp

@@ -687,7 +687,7 @@ Body2DSW::Body2DSW() :
 
 	still_time = 0;
 	continuous_cd_mode = Physics2DServer::CCD_MODE_DISABLED;
-	can_sleep = false;
+	can_sleep = true;
 	fi_callback = NULL;
 }