autofs: depend on host-nfs-utils

autofs: depend on host-nfs-utils

host-nfs-utils provides the host rpcgen utility. This fixes the build on
recent Fedora systems that removed rpcgen from the glibc package.

Fixes:
http://autobuild.buildroot.net/results/383/383bc8462f32a226645c9b792b8d65a25d74529d/
http://autobuild.buildroot.net/results/0c0/0c00f72512754b721813e13f0828d3a942f7b955/
http://autobuild.buildroot.net/results/50b/50b66d2a3c8264f618d7aa813b10050ed147209f/

Cc: Jonathan Ben Avraham <yba@tkos.co.il>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>