fixes broken D435i URDF due to upstream changes (realsense-ros release 2.2.14)

Apparently, upstream RealSense changes in ROS Melodic broke Stretch URDF creation. More information about the changes can be found using the following information:

+ realsense-ros release: https://github.com/IntelRealSense/realsense-ros/releases/tag/2.2.14
+ Debian package: ros-melodic-realsense2-description/bionic,now 2.2.14-1bionic.20200630.141906
+ relevant commit: f7cd5fced5

The corrected issue has to do with changes to "use_nominal_extrinsics" specified in the D435i xacros in the realsense2_description package.

The current commmit also changes the d435i launch file for Stretch (d435i_basic.launch) so that it no longer performs "initial_reset" by default. "initial_reset" appears to have resulted in long delays and freezing when bringing up the camera on the robot.

An excerpt from Intel's documentation for initial_reset follows:

"initial_reset: On occasions the device was not closed properly and due to firmware issues needs to reset. If set to true, the device will reset prior to usage." from https://github.com/intel-ros/realsense

stretch_calibration/nodes/update_uncalibrated_urdf.sh

@@ -6,4 +6,4 @@ echo ""
 
 echo "rosrun xacro xacro `rospack find stretch_description`/urdf/stretch_description.xacro > `rospack find stretch_description`/urdf/stretch_uncalibrated.urdf"
 
-rosrun xacro xacro `rospack find stretch_description`/urdf/stretch_description.xacro use_nominal_extrinsics:=true > `rospack find stretch_description`/urdf/stretch_uncalibrated.urdf
+rosrun xacro xacro `rospack find stretch_description`/urdf/stretch_description.xacro > `rospack find stretch_description`/urdf/stretch_uncalibrated.urdf

stretch_core/launch/d435i_basic.launch

@@ -55,7 +55,7 @@
          properly and due to firmware issues needs to reset. If set to
          true, the device will reset prior to usage."
          https://github.com/intel-ros/realsense -->
-    <arg name="initial_reset" value="true"/>
+    <!--<arg name="initial_reset" value="true"/>-->
     
     <!--<arg name="unite_imu_method" value="copy"/> linear_interpolation-->
   </include>

stretch_description/urdf/stretch_d435i.xacro

@@ -1,6 +1,7 @@
 <?xml version="1.0"?>
 <robot xmlns:xacro="http://www.ros.org/wiki/xacro" name="stretch_d435i">
-  
+
+  <xacro:arg name="use_nominal_extrinsics" default="true"/>
   <xacro:include filename="$(find realsense2_description)/urdf/_d435.urdf.xacro"/>
 
   <!-- xyz = "
@@ -8,12 +9,11 @@
        up and down (- down / + up)
        sideways (- right / + left)
        " -->
-  <xacro:sensor_d435 parent="link_head_tilt">
+  <xacro:sensor_d435 parent="link_head_tilt" use_nominal_extrinsics="$(arg use_nominal_extrinsics)">
     <origin
       xyz="0.03 -0.0122 0.0182"
       rpy="0.0 0.0 0.0" />
   </xacro:sensor_d435>
-
   
 </robot>