HPCC-8053 Superfile lock contention causing superfile corruption

Add/Remove and Swap file operations that keep the state
(list of subfiles) of the superfiles they deal with, could become
out of date, if they are blocked by other operations that hold
read locks when they try to get exclusive locks to manipulate them

The transaction mechanism temporarily releases locks to avoid
deadlock situations, when if/it regains, it must refresh state.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>