modify timing issue and add test case for DiscoveryManagerUnitTest

modify timing issue and add test case for DiscoveryManagerUnitTest

- default waiting time is 3sec as each test.
- change discovery checking way from using sleep method to condition_variable.
: just unlock waiting mutex when is called callback function.
- request multiple discovery that have equal contents, and just one canceled.
  other request will be received callback function.

modify createId's logic for RCSDiscoveryManagerImpl.

modify Sconscript
- directory location for DiscoveryMaanger' unittest code is changed.

Change-Id: I3dfd5b1440959eac200746eba098ebd1ff93b69b
Signed-off-by: doil.kwon <doil.kwon@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/3249
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>