GATT: Handle prepare_authorize parameter in WriteValue DBUS API

GATT: Handle prepare_authorize parameter in WriteValue DBUS API

In GATT Server role, prepare_authorize parameter will be set
when bluez wants authorization permission from the application when
ATT_PREPARE_WRITE_REQUEST PDU receive for the first time in case
of long write.

This is an initial patchset to parse prepare_authorize parameter from
bluez and avoid crash. Subsequent patches will be added to handle
authorization completely.

This patchset should be merged with the following bluez's patchset
in order to match API and avoid crash:
bluez Change-Id: I93bc46151ebbe695c74b224c3a3579c6e5d0de14

Change-Id: Ic4397ae86760177e08ccd283e80d4526bd32e0c4
Signed-off-by: Ayush Garg <ayush.garg@samsung.com>