Threads security context synchronization

Threads security context synchronization

- use lambda as signal handler
- return error if not all threads synced
- change NULL to nullptr
- added std::atomic_thread_fence for memory synchronization
- block SIGUSR1 signal during threads counting
- set signal set to empty
- added waiting loop for signal propagation
- reset signal handler after threads synced, not before
- synchronization of both: Smack labels and Linux capabilities

Change-Id: Ia9d6a503e88523c387ab1ba30e0e9a5a94f05a5c
Signed-off-by: Zbigniew Jasinski <z.jasinski@samsung.com>