udev-event.c: rename interface to <src>-<dest>, if <dest> taken

udev-event.c: rename interface to <src>-<dest>, if <dest> taken

e.g. if eth0 should be eth3 and eth3 is waiting to be renamed,
eth0 was renamed to eth0_rename. The kernel would take eth0 as the name
for a new interface and this new eth0 could also become eth0_rename, if
the target name is also taken. To prevent this name clash, the
interfaces are now renamed to <src>-<dest> and the rename is logged.