Revert "Remove unnecessary cast to string from 'verify_networks_resp's code"
Revert "Remove unnecessary cast to string from 'verify_networks_resp's code"

Unfortunately, `task.cache['args']['nodes']` contains nodes with integer-based UIDs, not string based. Hence, sets with UIDs are considered completely different and we consider all nodes are unreachable. That results to mistakingly setting "error" to "verify_network" task.

This reverts commit 8a0b8af085bd3654812661280befab71090353be.

Change-Id: Ie43bb2017021821b0342eef28e9ec4bd3542d22f
Closes-Bug: #1569140

stackforge/fuel-web,stackforge/fuel-web,stackforge/fuel-web