Fix linking of liboctbstack: conectivity_abstraction requires coap

Fix linking of liboctbstack: conectivity_abstraction requires coap

The order in which static libraries are listed matters, so
connectivity_abstraction needs to appear before coap.

This also solves the problem on iOS that caused libcoap to be moved to
later.

Change-Id: I0d4913955e3745b69672ffff13dbc5d38a438ef6
Signed-off-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/920
Reviewed-by: Charlie Lenahan <charlie.lenahan@intel.com>
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Caiwen Zhang <caiwen.zhang@intel.com>
Reviewed-by: Erich Keane <erich.keane@intel.com>