Rename cl_delta to control_joint_rad_to_cl

- This fixes the transition crash error, which seems to be related to
PX4#710 as well.
- While standard_vtol.sdf.jinja was updated to the new naming
convention, the standard_vtol_drop was not updated, this commit fixes
that.
- Also, PX4#730 is also relevant
for this issue.

models/standard_vtol_drop/standard_vtol_drop.sdf.jinja

@@ -739,7 +739,7 @@
       <control_joint_name>
         left_elevon_joint
       </control_joint_name>
-      <cl_delta>-1.0</cl_delta>
+      <control_joint_rad_to_cl>-1.0</control_joint_rad_to_cl>
       <robotNamespace></robotNamespace>
       <windSubTopic>world_wind</windSubTopic>
     </plugin>
@@ -761,7 +761,7 @@
       <control_joint_name>
         right_elevon_joint
       </control_joint_name>
-      <cl_delta>-1.0</cl_delta>
+      <control_joint_rad_to_cl>-1.0</control_joint_rad_to_cl>
       <robotNamespace></robotNamespace>
       <windSubTopic>world_wind</windSubTopic>
     </plugin>
@@ -783,7 +783,7 @@
       <control_joint_name>
         elevator_joint
       </control_joint_name>
-      <cl_delta>-12.0</cl_delta>
+      <control_joint_rad_to_cl>-12.0</control_joint_rad_to_cl>
       <robotNamespace></robotNamespace>
       <windSubTopic>world_wind</windSubTopic>
     </plugin>