iptablesPrivateChainCreate: Rename @tmp variable

iptablesPrivateChainCreate: Rename @tmp variable

The iptablesPrivateChainCreate() function gets a NULL terminated
array of strings (@lines argument), each item representing one
line of iptables output. Currently, the variable used to iterate
over the array is named 'tmp' which is not very descriptive.
Rename it to 'line'.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Tested-by: Jaroslav Suchanek <jsuchane@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>