Bug#1110704: Bug#1100100: postfix: configure-instance's cp call fails on overlayfs over nfs4

[Michael Tokarev]

See 
https://salsa.debian.org/postfix-team/postfix-dev/-/commit/d4e1171ae6a79d36e7121bb0698eef3bd3f2498b
for the solution I plan to use.

There are 2 bugs filed about this issue, #1110704 and #1100100.
Thanks,

/mjt