tests: bootstrap-aio: Add sftp subsystem option for SUSE
tests: bootstrap-aio: Add sftp subsystem option for SUSE

Convert the existing sftp variable into a dictionary so it can contain
the correct sftp path for SUSE hosts.

Change-Id: Ie5ade74f9fc5a6fa8eef4af35b269d87125674d6

yanyao/openstack-ansible,stackforge/os-ansible-deployment,cfarquhar/openstack-ansible,bunchc/openstack-ansible,openstack/openstack-ansible,cfarquhar/openstack-ansible,bunchc/openstack-ansible,yanyao/openstack-ansible,openstack/openstack-ansible,stackforge/os-ansible-deployment