We change the behaviour of recursive acl set to not lock the entire directory
tree but doing read lock during find and individual write locks while setting
ACLs. While this means that a directory that is created during the time between
a reader lock and after the parent directory of the new directory will not see
the new ACL, while the previous behaviour will not allow any directory creation
to happen during. Where that level of consistency is needed, we have the
`--with-synchronous-write-lock` switch which will lock the whole instance and
apply acls recursively.

Fixes: EOS-5554


Signed-off-by: Abhishek Lekshmanan <abhishek.lekshmanan@cern.ch>