cli: allow setting multiple IPs in bond 'arp_ip_target' option

cli: allow setting multiple IPs in bond 'arp_ip_target' option

The bond 'arp_ip_target' option contains a list of comma-separated IP
addresses; but comma is also used to separate options and so at the
moment it is not possible to specify multiple IPs as the command

 $ nmcli c m b1 bond.options \
   mode=0,arp_interval=1,arp_ip_target=1.1.1.1,2.2.2.2

interprets 2.2.2.2 as the next option.

Allows spaces to be used as separators for the IPs of the
'arp_ip_target':

 $ nmcli c m b1 bond.options \
   "mode=0,arp_interval=1,arp_ip_target=1.1.1.1 2.2.2.2"