Since some commands access both Maildirs and IMAP/NNTP servers
at the same time, LeiPmdir may see the same lei->{auth} and
lei->{net} objects as the sibling LeiInput-based workers.
Delete those at fork and do not attempt to do authentication in
those cases, since "net_merge_continue" will not be a registered
op and cause PktOp to fail even if authentication /can/ work
from a LeiPmdir worker.