Uninstaller: call usage if incorrect number of options are provided (#556)

This PR improves the user experience when using the uninstall script to
include usage output when an incorrect number of options are provided to
the script.

Signed-off-by: Kathryn Baldauf <k_baldauf@apple.com>

scripts/uninstall-container.sh

@@ -49,6 +49,7 @@ done
 
 if [ $OPTS != 1 ]; then 
     echo "Invalid number of options. Must provide either -d OR -k"
+    usage
     exit 1
 fi