fix(storage): avoid error in storage actions (hot-fix)

[joseivanlopez]

Problem

Generating storage actions crashes, see:

• https://github.com/openSUSE/agama/issues/1396
• https://github.com/openSUSE/agama/pull/1379

Solution

Avoid actiongraph clean-up by the ruby GC.

Note: This is a hot-fix. A better solution is required.