initrd: fix generation of MTU and cloned-mac-address for masters
Setting a MTU or a cloned MAC for bonds/bridges/teams fails with:
# nm-initrd-generator -- bond=bond0:eno1,eno2:mode=802.3ad
ip=192.168.1.5::192.168.1.254:255.255.255.0:MyServer:bond0:none::01:02:03:04:05:06
bootdev=bond0 nameserver=192.168.1.1
<warn> cmdline-reader: 'bond' does not support setting cloned-mac-address
Fix this.