csapi-sensor: fix bug about the lifetime of delegate

csapi-sensor: fix bug about the lifetime of delegate

When the callback is passed to the native layer using PInvoke,
the lifetime of delegate has to be considered.
if the member function is passed to the interop directly, the memory
allocated within this function is not managed by the GC.

Change-Id: I06ab30b0e62c1f4baba5bcb38dd75f9764a3b0d5
Signed-off-by: kibak.yoon <kibak.yoon@samsung.com>