BUF:Ignore exception when closing connection

In Linux/Unix, pexpect connection.close() call will
throw an ExceptionPexpect exception if connection is already terminated.

Catch and log the exception to avoid crashing.

OSEHRA-Id: http://issues.osehra.org/browse/VAF-78
Change-Id: Id81fa66bcd6a2390ded69669758c63deb41cdbae