Inconsistent root after erroring calls

[ureeves]

Describe the bug
The root is inconsistent after an erroring call.

To Reproduce
During the implementation of dusk-network/rusk#1125, a test was added that makes an erroring call, and then subsequently executes another call. Another session is then instantiated that only runs successful calls, which then displays a different root than before.

Expected behaviour
Calls should be atomic - if they error nothing should be left behind.

[ureeves]

This issue has been reproduced in #293 and the solution has been identified.