Change the APP_NAME to Packstack

Instead of 'Welcome to Installer setup utility' it should be
'Welcome to the Packstack setup utility'.

Change-Id: I698d17645f4a53ce738be5ea463335466408ed6e
(cherry picked from commit 85ceabbfaf0e6cac1c733bc02a0a291087cb4cc0)
Merge "Change the APP_NAME to Packstack" into juno