spin in a loop eating CPU time. This bug has existed since the
TI-RPC import. The problem is that we should only enter the select
loop if at least one TCP server was started. Fix this by having
the master nfsd become a UDP server itself if there are no TCP
servers.
Also improve/correct the code for cleaning up slave nfsd processes
and unregistering with rpcbind when the master nfsd exits.
One issue that remains open is that if a slave nfsd dies, then all
nfsds will shut down. This is because nfssvc() in the master nfsd
returns 0 when the master nfsd receives a SIGCHLD.
Submitted by: tmm
fef7dd5a5f