bash: fix pip install issue with jjb-sandbox-env function

- In a new system (e.g. ubuntu 18.04 docker image), the pip3
  installation of jenkins-job-builder fails unless pip3 wheel
  is completed on a previous pip3 install command.

Type: fix

Change-Id: I4354c851161b9c470d44951dc8b722ffc87f56f7
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>

extras/bash/functions.bash

@@ -229,7 +229,8 @@ jjb-sandbox-env()
     rm -rf $VENV_DIR \
        && python3 -m venv $VENV_DIR \
        && source $VENV_DIR/bin/activate \
-       && pip3 install wheel jenkins-job-builder==3.0.2
+       && pip3 install wheel \
+       && pip3 install jenkins-job-builder==3.0.2
 
     alias jjsb='jenkins-jobs --conf $JENKINS_INI'
     function jjsb-test() {