The property test for the mRandomNodes function revealed that it may
sometimes pick out a sample of fewer than m nodes even when the number
of nodes to pick from (excluding the local node) is >= m. Rewrite it
using a random shuffle or permutation so that it always picks a
uniformly-distributed sample of the requested size whenever the
population is large enough.
Signed-off-by: Cory Snider <csnider@mirantis.com>