test.cfg.ethtool: Update guest realted params

Update ethtool params for different guest and driver
Signed-off-by: NAmos Kong <akong@redhat.com>
Signed-off-by: NXiaoqing Wei <xwei@redhat.com>

tests/cfg/ethtool.cfg

-- ethtool: install setup image_copy unattended_install.cdrom
+- ethtool:
     virt_test_type = qemu libvirt
     only Linux
+    no rtl8139
+    no RHEL.3.9
     type = ethtool
     filesize = 512
+    nic_mode = tap
+    supported_features = "tx rx sg tso"
+    RHEL.4:
+        e1000:
+            supported_features = "tx rx sg tso"
+        virtio_net:
+            supported_features = "tx sg tso"
+    RHEL.5:
+        e1000:
+            supported_features = "tx rx sg tso gso"
+        virtio_net:
+            supported_features = "tx sg tso gso"
+    RHEL.6:
+        # gso gro lro is only supported by latest kernel
+        e1000:
+            supported_features = "tx rx sg tso gso gro lro"
+        virtio_net:
+            supported_features = "tx sg tso gso"