network-legacy: Support for static Wicked configuration

[tacerus]

Hi,

this introduces the ip=wicked-static cmdline option, allowing to apply a static network configuration from the full OS in the initramfs.

General remarks:

• Changes to cmdline parameters are not ideal, as they go against the upstream concept of keeping dracut distribution agnostic - unfortunately I did not find an existing way to introduce a static backend - the existing functions and arguments seemed to only cover DHCP as well as static configuration passed using cmdline options.
• I experimented with porting the XML schemas and libraries needed for native Wicked ifup functionality to the initramfs, however going the route with this patch, using the existing do_static functionality, seemed more lightweight.
• Code style: I did not find any styling guides for dracut. The existing code seemed to be arbitrarily styled - for example in some places there is be a space before semicolons, in other places there isn't, and in some places variables are be quoted, in others they are not. Hence I picked a combination of what seemed like the most common style in the document.

Functionality remarks:

• The implementation introduced with this patch only applies the first/primary interface address. Additional IP addresses (IPADDR_xxx) are not covered. I deemed the added complexity of iterating over additional addresses not crucial enough for now.
• The implementation covers /etc/sysconfig/network/ifcfg-* and /etc/sysconfig/network/config files copied upon buildtime. I hope it is clear enough to a user who is reading the manpage, that changes to these files require a run of mkinitrd in order for them to be applied to the initramfs.

Testing remarks:
I tested this with the following sample /etc/sysconfig/network/ifcfg-enp1s0 files:

• Test 1 (generated by YaST's LAN module):

IPADDR='192.168.5.14/24'
IPADDR_1='2a02:1748:f7df:9c80::aa1/64'
BOOTPROTO='static'
STARTMODE='auto'
LABEL_1='IPv6'
ZONE='public'

• Test 2:

IPADDR='192.168.5.14'
PREFIXLEN='24'
IPADDR_1='2a02:1748:f7df:9c80::aa1/64'
BOOTPROTO='static'
STARTMODE='auto'
LABEL_1='IPv6'
ZONE='public'

• Test 3:

IPADDR='192.168.5.14'
NETMASK='255.255.255.0'
IPADDR_1='2a02:1748:f7df:9c80::aa1/64'
BOOTPROTO='static'
STARTMODE='auto'
LABEL_1='IPv6'
ZONE='public'

• Test 4:

IPADDR_1='192.168.5.14'
PREFIXLEN_1='24'
IPADDR='2a02:1748:f7df:9c80::aa1/64'
BOOTPROTO='static'
STARTMODE='auto'
LABEL_1='IPv4'
ZONE='public'

all of them in combination with the following /etc/sysconfig/network/config snippet:

NETCONFIG_DNS_STATIC_SEARCHLIST="home.lysergic.dev"
NETCONFIG_DNS_STATIC_SERVERS="192.168.5.1 2a02:1748:f7df:9c80::1"

I hope to have covered all relevant points.

Best,
Georg