VCL: improve debug output

- Refactor debug output to include vpp handle associated
  with session id where appropriate.
- Fix vcom_connect return value on error.
- Refactor vcom_socket_epoll_pwait().
- Fix sock_test_server/client connect failure handling.

Change-Id: I2649596aa4b8a77d9bd876409a76810cb2785797
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>
diff --git a/src/vcl/vppcom.h b/src/vcl/vppcom.h
index 55710b7..5511f04 100644
--- a/src/vcl/vppcom.h
+++ b/src/vcl/vppcom.h
@@ -64,6 +64,7 @@
   VPPCOM_EINVAL = -EINVAL,
   VPPCOM_EBADFD = -EBADFD,
   VPPCOM_EAFNOSUPPORT = -EAFNOSUPPORT,
+  VPPCOM_ECONNABORTED = -ECONNABORTED,
   VPPCOM_ECONNRESET = -ECONNRESET,
   VPPCOM_ENOTCONN = -ENOTCONN,
   VPPCOM_ECONNREFUSED = -ECONNREFUSED,
@@ -120,6 +121,10 @@
       st = "VPPCOM_EAFNOSUPPORT";
       break;
 
+    case VPPCOM_ECONNABORTED:
+      st = "VPPCOM_ECONNABORTED";
+      break;
+
     case VPPCOM_ECONNRESET:
       st = "VPPCOM_ECONNRESET";
       break;