ONOS-3791 NETCONF session factory and exception on device connection

Change-Id: I7c6651a4f76537056a2dc8f94d54818b5b238b9a
diff --git a/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java b/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
index ea3bfcc..4901c13 100644
--- a/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
+++ b/providers/netconf/device/src/main/java/org/onosproject/provider/netconf/device/impl/NetconfDeviceProvider.java
@@ -46,6 +46,7 @@
 import org.onosproject.netconf.NetconfDevice;
 import org.onosproject.netconf.NetconfDeviceInfo;
 import org.onosproject.netconf.NetconfDeviceListener;
+import org.onosproject.netconf.NetconfException;
 import org.slf4j.Logger;
 
 import java.io.IOException;
@@ -190,10 +191,11 @@
                                                                        addr.ip(),
                                                                        addr.port()));
                                      } catch (IOException e) {
-                                         log.info("Can't connect to NETCONF " +
-                                                          "device on {}:{}",
-                                                  addr.ip(),
-                                                  addr.port());
+                                         throw new RuntimeException(
+                                                 new NetconfException(
+                                                         "Can't connect to NETCONF " +
+                                                                 "device on " + addr.ip() +
+                                                                 ":" + addr.port(), e));
                                      }
                                  }
                         );