Enable allowerasing in undercloud upgrade from wallaby
Enable allowerasing in undercloud upgrade from wallaby

After adding python-sqlalchemy13 in Wallaby [1], the upgrade process
need to remove python3-sqlalchemy13 package to install
python3-sqlalchemy-1.4. This can be handled by dnf but requires to
enable the option --allowerasing which is disabled by default:

[1] https://review.rdoproject.org/r/c/rdoinfo/+/45546

Closes-Bug: #1992305
Change-Id: I4070723741fdf8e5dc27e93f620d7206b6e7893c

openstack/tripleo-heat-templates,openstack/tripleo-heat-templates