[Bug] Protostuff serialization protocol not support for java.sql.Date

[fitzf]

• I have searched the issues of this repository and believe that this is not a duplicate.
• I have checked the FAQ of this repository and believe that this is not a duplicate.

Environment

• Dubbo version: 2.7.2
• Operating System version: OSX
• Java version: 1.8

Steps to reproduce this issue

@Test
public void testSerializeSqlDate() throws IOException, ClassNotFoundException {
    java.sql.Date originTime = new java.sql.Date(System.currentTimeMillis());
    this.protostuffObjectOutput.writeObject(originTime);
    this.flushToInput();

    java.sql.Date serializedTime = protostuffObjectInput.readObject(java.sql.Date.class);
    assertThat(serializedTime, is(originTime));
}

Expected Result

What do you expected from the above steps？

Actual Result

Expected: is <2019-06-25>
   but: was <1970-01-01>
Expected :is <2019-06-25>
  Actual   :<1970-01-01>

If there is an exception, please attach the exception trace: