Fix the build failures on Ubuntu 12.04 32-bit machine.

Fix the build failures on Ubuntu 12.04 32-bit machine.

Changes incorporate inclusion of "condition_variable" header file
in notification-manager dir.

Change-Id: I8dcf2a54579d8c5a1ce9f60a6498007eb7fe2c37
Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/2809
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Hun-je Yeon <hunje.yeon@samsung.com>
Reviewed-by: Younghyun Joo <yh_.joo@samsung.com>
Reviewed-by: Madan Lanka <lanka.madan@samsung.com>