xsh_ping.c:  Fix argument parsing
xsh_ping.c:  Fix argument parsing

The 'ping' shell command did not parse its arguments correctly and would
use the IPv4 'target' address uninitialized if any options were specified
but a destination address was not.

ZeroTau/xinu,osa1/osdev,robert-w-gries/xinu,ZeroTau/xinu,osa1/osdev,robert-w-gries/xinu,rahsinha2/XINU-OS,ZeroTau/xinu,rahsinha2/XINU-OS,robert-w-gries/xinu,rahsinha2/XINU-OS,osa1/osdev