What does this MR do?
Extracts all volumes management from docker executor struct to a separate one.
Why was this MR needed?
First step for providing #3909 (closed).
Are there points in the code the reviewer needs to double check?
Does this MR meet the acceptance criteria?
Added tests for this feature/bug
In case of conflicts with
master- branch was rebased
What are the relevant issue numbers?
Part of #3909 (closed)