app/testpmd: revert softnic integration in CLI thread

app/testpmd: revert softnic integration in CLI thread

This patch reverts the testpmd CLI prompt routine modifications done
in order to support softnic.
The reason of doing so is due to testpmd abnormal exit observed on
several setups caused by the softnic modifications to this routine,
for example: When running testpmd with tap interface
(testpmd
 -n 4 --vdev=net_tap0,iface=tap0,remote=eth1 -- --burst=64
 --mbcache=512 -i --nb-cores=7 --rxq=2 --txq=2 --txd=512
 --rxd=512 --port-topology=chained --forward-mode=rxonly)
testpmd crashes seconds after presenting its prompt with the following
error:
  testpmd> PANIC in prompt():
  CLI poll error (-1)

  Thread 1 "testpmd" received signal SIGABRT, Aborted.
  0x00007ffff668e0d0 in raise () from /lib64/libc.so.6
  (gdb) bt
  #0  0x00007ffff668e0d0 in raise () from /lib64/libc.so.6
  #1  0x00007ffff668f6b1 in abort () from /lib64/libc.so.6
  #2  0x0000000000468027 in __rte_panic ()
  #3  0x00000000004876ed in prompt ()
  #4  0x000000000046dffc in main ()

When running testpmd with bare-metal device
(testpmd -n 4 --socket-mem=1024,1024 -w 04:00.0  --
 --burst=64 --mbcache=512 -i --nb-cores=7
 --rxq=64 --txq=4 --txd=16 --rxd=16)
and pressing CTRL+D right after testpmd prompt is presented then
the program crashes while presenting the same messages as above.

Needless to say that this behavior is not observed when using the
previous CLI prompt routine.

Fixes: 0ad778b398c6 ("app/testpmd: rework softnic forward mode")

Signed-off-by: Moti Haimovsky <motih@mellanox.com>
Acked-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Acked-by: Aaron Conole <aconole@redhat.com>