Expose PISetup() API in Plugin Interface.

Expose PISetup() API in Plugin Interface.

This puts the onus on the application layer to perform discovery
operations for their radio(s).  This way the discovery operations can be
triggered via the appropriate actions for the application.

Change-Id: If5140b436159c74260dc30ac3d33401e62478b25
Signed-off-by: Joseph Morrow <joseph.l.morrow@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3779
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Jon A. Cruz <jonc@osg.samsung.com>