tests: remove flaky test code in TestMachinesStoragePools
tests: remove flaky test code in TestMachinesStoragePools

It used to check for disabled attribute on the 'Activate' button after
being clicked.

We can't deterministically make the activation operation take X
seconds and therefore that check was always prompt to flakiness.

garrett/cockpit,mvollmer/cockpit,garrett/cockpit,cockpit-project/cockpit,mvollmer/cockpit,martinpitt/cockpit,garrett/cockpit,martinpitt/cockpit,cockpit-project/cockpit,martinpitt/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,garrett/cockpit,cockpit-project/cockpit,garrett/cockpit,martinpitt/cockpit,mvollmer/cockpit,mvollmer/cockpit