fix(multipath): remove dependency on multipathd.socket

fix(multipath): remove dependency on multipathd.socket

This reverts commit e39ff407eca1d783ab44093c44db5ee401ff5b1d, removes
an incorrect `Also=` directive from multipathd.service.

`Also=multipathd.socket` is not the correct behavior for a
socket-activated service. This directive has been removed upstream
and dracut should do the same.

This fixes #2289, #2175 where in the cleanup hook running multipath
binary triggers activation of multipathd.service after it is stopped
as dracut prepares to switch root in initrd-cleanup.service.