HPCC-10481 - Dynamic group leaves groupType uninitialized

A DFS lookup of a dynamic group, e.g. a ip set, left the
referene groupType uninitialized. Consequently it could caused
out of range array lookups into the default replication paths.
This happened when the replication directory of the
ClusterPartDiskMapSpec of a ClusterInfo instance was setup
which was introduced by the previous commit of this issue.

Default groupType to grp_unknown if lookup group based on
ip's.

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>