examples/vhost: fix guide

examples/vhost: fix guide

Fix typos in sample console commands.
Remove "user@target:~$" prefixes in command lines.

Add --socket-mem 1024 to vhost-switch command lines.
Without the --socket-mem parameter all hugepages will be allocated
to vhost-switch, leaving no memory for the VM.

Add --disable-hw-vlan-filter parameter to testpmd command lines.
Without this parameter testpmd fails on startup in the VM.

Increase value of --sock-mem parameter to testpmd as original
value was too small.

Fixes: d0dff9ba445e ("doc: sample application user guide"
Fixes: 9bc23cb8209c ("doc: add vhost-user to sample guide")
Fixes: 43866bf71d58 ("doc: fix vhost sample parameter")

Signed-off-by: Bernard Iremonger <bernard.iremonger@intel.com>
Acked-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>