vpp-swan: change flow in function for add route

This patch addresses the issue when the list of available interfaces
is not up to date. Due to this issue adding a new route fails
and finally the connection is not established.

Type: fix
Signed-off-by: Gabriel Oginski <gabrielx.oginski@intel.com>
Change-Id: I3a63c0dd99ebc28ea149b4b23867440937682761
diff --git a/extras/strongswan/vpp_sswan/kernel_vpp_shared.h b/extras/strongswan/vpp_sswan/kernel_vpp_shared.h
index c699d49..7e8d203 100644
--- a/extras/strongswan/vpp_sswan/kernel_vpp_shared.h
+++ b/extras/strongswan/vpp_sswan/kernel_vpp_shared.h
@@ -15,6 +15,14 @@
  * limitations under the License.
  */
 
+/**
+ * Every 2 seconds, the thread responsible for collecting the available
+ * interfaces will be executed.
+ * Retrying 5 times every 1 second ensures that there is enough time to check
+ * if the interface will be available.
+ */
+#define N_RETRY_GET_IF 5
+
 typedef struct vac_t vac_t;
 
 /**