Bug: tools: Fix moving a resource with a lifetime constraint

A node can be specified two different ways - with attribute="#uname"
and value= on an expression XML node, or with node= on a rsc_location
XML node. Both possibilities need to be considered when attempting to
clear an existing constraint.

cli_resource_clear was previously only considering the second case.
This patch rearranges the code to allow for trying both, and then adds
the code to try the first case by constructing a different blob of XML
to match.

See rhbz#1648620