Fix issue with multicast prescence subscriptions

Fix issue with multicast prescence subscriptions

After registering for a multicast presence, the callback handler URI,
that is searched for isn't completley formed, so callbacks don't happen.

Made uri format consistent across unicast and multicast.
Updated C++ sample app presenceclient.cpp for multicast presence cases.
Also removed repeat test case in presenceclient.cpp PrintUsage().
Updated 2 files in the service directory for multicast presence cases.
Added test in C sample occlient.cpp for a multicast presence
subscription.
Modified OCPlatform.h::subscribePresence() documentation to inform api
users of the expected format.

Change-Id: Ic1a262566f605dd0882e563b4ee2d03bd21016be
Signed-off-by: Charlie Lenahan <charlie.lenahan@intel.com>
Signed-off-by: Mandeep Shetty <mandeep.shetty@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/787
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Sashi Penta <sashi.kumar.penta@intel.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>
Tested-by: Uze Choi <uzchoi@samsung.com>