Remove entry-point for element-info

This is really an internal dib tool.  Move it to the lib directory,
and call it with the python we are running under.

This is one less reason to require the virtualenv to be activated when
you run 'disk-image-create'.

Change-Id: Id689683a0b1fdcb446b04ba967284a216133d743

diskimage_builder/lib/common-functions

@@ -340,7 +340,7 @@ function arg_to_elements() {
   #        element=$i
   #        path=${image_elements[$i]
   #      done
-  elinfo_out="$(element-info --env $IMAGE_ELEMENT)"
+  elinfo_out="$(${DIB_PYTHON_EXEC} ${_LIB}/element-info.py --env ${IMAGE_ELEMENT})"
   if [ $? -ne 0 ]; then
       echo "ERROR: element-info failed to expand elements."
       exit 1

diskimage_builder/lib/element-info.py

@@ -0,0 +1,7 @@
+import sys
+
+from diskimage_builder.element_dependencies import main
+
+
+if __name__ == "__main__":
+    sys.exit(main())

setup.cfg

@@ -32,7 +32,6 @@ data_files =
 
 [entry_points]
 console_scripts =
-    element-info = diskimage_builder.element_dependencies:main
     dib-block-device = diskimage_builder.block_device.cmd:main
     disk-image-create = diskimage_builder.disk_image_create:main
     ramdisk-image-create = diskimage_builder.disk_image_create:main