KmsHttpEPServer: Make stop server callback execute in internal thread

Change-Id: I75f21dc6c14ccc89df7d54e79a7c8fe31f4cb0b7
KmsHttpEPServer: Provide user data to callbacks

Change-Id: I7e44277826f3f2a6959976a9c57c0da39e2db0c0
KmsHttpEPServer: Execute register function from internal loop

Change-Id: I1fa77cf8ba6a5c9ac87e0d34280511979581e742
KmsHttpEPServer: Execute callbacks in next loop iteration if it is not the same thread

Change-Id: I86cf46d44effed49a8f9455bbff500bd49290414
HttpEndpointImpl: small fixes

Change-Id: I15d853d1e90063df0cb81b39627cbbf07d3681b1
KmsHttpEPServer: Make unregister operation in internal thread

Change-Id: I0eab87bdfc9683f92710d1c8aaac89e25b12b6c7
KmsHttpLoop: Synchronize thread execution using condition variables

Change-Id: I5d69b31ec548528969fdc7d82f9df54620b2cfc5