We previously fixed a bunch of places, but not quite *all* the places;
at the very least, some account-layer services (like the replicator and
auditor IIRC) could still bomb out -- and it's important that
replicators still respect fallocate_reserve!
Now, do the NicerInterpolation thing every time we call readconf.
Additionally, clean up the original fix to avoid globally
monkey-patching configparser.
Related-Bug: #1844368
Closes-Bug: #1872553
Change-Id: I4512e686cde37930f0482909f537220a57fef76b
(cherry picked from commit 2854eddb44)