Split setup-passwords into undercloud and overcloud

Don't assume overcloud and undercloud can access the same file to get
the passwords from. Split up setup-passwords so
setup-undercloud-passwords is used in devtest_undercloud and
setup-overcloud-passwords is used in devtest_overcloud.

Change-Id: I47de68d081ab3d8e83d014d416e229c055b42ec8
Merge "Split setup-passwords into undercloud and overcloud"