[DEV](iOS) fix unconnected read return error code
[DEV](iOS) fix unconnected read return error code

Change-Id: I6399c318a4850cdba922d1353b3898bf1626b317
Reviewed-on: https://gerrit.parrot.biz/39840
Reviewed-by: Maxime Maitre <e46fe1f9761923e97d4fbff83ab76adb16770b5c@parrot.com>

Parrot-Developers/libARSAL,Parrot-Developers/libARSAL,Parrot-Developers/libARSAL