Remove support of "MD_SAL" node and node connector type.

MD-SAL got to use the same node and node connector type as AD-SAL for
OpenFlow switch and port.

Change-Id: I738f705908d8fa363195fa42e3ab1fa90585fe24
Signed-off-by: Shigeru Yasuda <s-yasuda@da.jp.nec.com>