udev/net: fix assignment of ID_NET_NAME=

udev/net: fix assignment of ID_NET_NAME=

E.g. sd_device object of network interface 'hoge!foo' has sysname 'hoge/foo'.
So, previously udevd assigned 'hoge/foo' rather than 'hoge!foo' to ID_NET_NAME,
hence even when renaming is not requested, such interface was renamed to 'hoge_foo'
(note '/' cannot be used in network interface name, hence escaped to underbar).