Enhance logging in NetconfSessionImpl

There are a few places where Throwable.getMessage() is emitted directly
instead of utilizing a Throwable argument to the Logger output methods.
Using debug as an example, when dealing with exception reporting cases,
it is, generally better to rely upon:

http://www.slf4j.org/api/org/slf4j/Logger.html#debug(java.lang.String, java.lang.Throwable)

than:

http://www.slf4j.org/api/org/slf4j/Logger.html#debug(java.lang.String)

This commit also cleans up the language of another log message.

Change-Id: I53a77286069c112aafc83ad8157a439a4d50e52e
Signed-off-by: Ryan Goulding <ryandgoulding@gmail.com>
diff --git a/protocols/netconf/ctl/src/main/java/org/onosproject/netconf/ctl/NetconfSessionImpl.java b/protocols/netconf/ctl/src/main/java/org/onosproject/netconf/ctl/NetconfSessionImpl.java
index b080b4e..29a5dfc 100644
--- a/protocols/netconf/ctl/src/main/java/org/onosproject/netconf/ctl/NetconfSessionImpl.java
+++ b/protocols/netconf/ctl/src/main/java/org/onosproject/netconf/ctl/NetconfSessionImpl.java
@@ -129,8 +129,8 @@
                             deviceInfo.name(), deviceInfo.password());
                 }
             } catch (IOException e) {
-                log.error("Authentication connection to device {} failed: {} ",
-                          deviceInfo.getDeviceId(), e.getMessage());
+                log.error("Authentication connection to device {} failed",
+                          deviceInfo.getDeviceId(), e);
                 throw new NetconfException("Authentication connection to device " +
                                                    deviceInfo.getDeviceId() + " failed", e);
             }
@@ -154,7 +154,7 @@
             this.addDeviceOutputListener(new NetconfDeviceOutputEventListenerImpl(deviceInfo));
             sendHello();
         } catch (IOException e) {
-            log.error("Failed to create ch.ethz.ssh2.Session session." + e.getMessage());
+            log.error("Failed to create ch.ethz.ssh2.Session session.", e);
             throw new NetconfException("Failed to create ch.ethz.ssh2.Session session with device" +
                                                deviceInfo, e);
         }
@@ -246,7 +246,7 @@
             try {
                 startSshSession();
             } catch (IOException e) {
-                log.debug("The connection with {} had to be reopened", deviceInfo.getDeviceId());
+                log.debug("The connection with {} was reopened", deviceInfo.getDeviceId());
                 try {
                     startConnection();
                 } catch (IOException e2) {