Make dowload provider run properly with multi-user and on 64 bit architecture

Make dowload provider run properly with multi-user and on 64 bit architecture

bug fixes:
 - get smack fs path from smack API
 - use int type with ioctl FIONREAD to get correct values on both 64 and 32 bits arches
 - fixed wrong usage of smack_new_label_from_socket
 - moved management of default destination to CAPI in order to run the code
with user privileges
 - removed code trying to guess remaining disk space because it only checked an
unreachable, hard coded folder instead of real destination. The case when the disk
is full is already handled at writing time.
 - added dependency on net-config (in specfile) because DP can't work properly
without it.

Bug-Tizen: TC-1409
Bug-Tizen: TC-1415
Change-Id: Ib98cabfd074313e2ac37300ce1af5e318de6327f
Signed-off-by: Romuald Texier-Marcadé <romuald.texier-marcade@open.eurogiciel.org>