dracut-module-setup: Support the network for ipv6 protocol
    
    Previously, Kdump will save route to setup the network route in the 2nd
    kernel for ipv4 protocol. To support ipv6 protocol, make Kdump fetch
    correct nexthop, since the ruturning format is different.
    
    In order to enhance kdump to support ipv6, support the static ip for
    ipv6 protocol, which ipv4 has supported already.
    
    Introduce a new lib function get_remote_host which is used to factor out
    the ip address(ipv4 or ipv6) and hostname in /etc/kdump.conf.
    
    Introduce a new lib function is_ipv6_address which is used to make sure
    whether the passed ip address is ipv4 or ipv6.
    
    Introduce a new lib function is_hostname which is used to confirm
    whether the passed parameter is hostname, not the ip address.
    
    Introduce a new function get_ip_route_field which is used to factor out
    the specified string in ip route info.
    
    Due to the different format between ipv4 and ipv6 protocol, quote the
    ipv6 address with bracket "[]" to make dracut notify.
    
    Signed-off-by: Minfei Huang <mhuang@redhat.com>
    Acked-by: Dave Young <dyoung@redhat.com>