Fix for IOTCLT-212
Fix for IOTCLT-212

This commit includes
 - Fix for IOTCLT-212 : Observation notification behaves differently depending on observe option length

ARMmbed/mbed-client,tridonic-com/mbed-client,tridonic-com/mbed-client,tridonic-com/mbed-client,ARMmbed/mbed-client,ARMmbed/mbed-client