Allow updates to /opt/stack/etc/profile.cfg on backend nodes without re-install

[anooprajendra]

When an attribute is added/removed/updated, /opt/stack/etc/profile.cfg on a backend node is not updated. The only way to update it is to re-install the machine.

Since quite a few processes depend on using profile.cfg for their attributes, and since the "stack" command line does NOT exist on a backend node, the user shouldn't be required to re-install a backend node just to update a bunch of attributes.

Related to #146

[jlkaiser]

Poor man's pillars? What does this get used for?

There is a "stack sync host file" in stacki-tools that could be made to do this.