qa: refactor some tests to share common discovery logic
pmdalinux: support for the additional nfs v4.1 operations

All NFS instance array definitions are also updated such that
the size macros are used in the definition, giving us better
compile-time checking that the values arrays (proc_net_rpc.h)
match up with the instance domains (pmda.c).

Thanks to Marko for pointing out these missing operations.