nfs-utils: add support for inotify
rpc.idmapd needs dnotify support, however dnotify is replaced by inotify, so dnotify is not enabled in the alpine kernel.
There is a patch for inotify support for nfs-utils:
https://patchwork.kernel.org/patch/9802949/
It does not seem to be applied upstream, but we should consider taking it in.
(from redmine: issue id 7599, created on 2017-07-24, closed on 2017-11-30)