Add logs and error handling codes for sensor listener

Add logs and error handling codes for sensor listener

If listener connection is failed, it should be handled as an error.
Previously, if connection is failed, it is not handled and treated as
success.
To handle 'connection failure' situation, return statement and state
member variable(indicates if sensor_listener is successfully
initialized) are added.

Change-Id: I4801ac7fb78cbbf1dea7808eed3ba84e9f3ab362
Signed-off-by: SangYoun Kwak <sy.kwak@samsung.com>