unfs3: fixed the issue that unfsd consumes 100% CPU

unfs3: fixed the issue that unfsd consumes 100% CPU

The 'accept' function on the socket of unfsd daemon
is always in below error state:
accept(4, 0x7ffd5e6dddc0, [128]) = -1 EINVAL (Invalid argument)
accept(6, 0x7ffd5e6dddc0, [128]) = -1 EINVAL (Invalid argument)

And 'strace -c -p <the pid of unfsd>' shows:
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 70.87    0.005392           0    513886    513886 accept
 29.13    0.002216           0    256943           poll

This error state is in the 'for' loop of the daemon, so it consumes 100%
CPU. The reason is that 'listen' is not called for the TCP socket before
'accept'. Actually the called 'svc_tli_create' from libtirpc will not call
'listen' on a bound socket.

Signed-off-by: Haiqing Bai <Haiqing.Bai@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>