THRIFT 3089 - stop adding period before enum name unless java namespace is provided

[mreve]

Using the example from issue's description:

IDL file contains:

struct Params {
    1: optional Color bColor = Color.BLACK; 
}

Compiled to java (no namespace):

public Params() {
    this.bColor = .Color.BLACK;
}

How it looks like with namespace enumtest:

public Params() {
    this.bColor = enumtest.Color.BLACK;
}

This fix prevents adding the period sign when there's no java namespacec provided in the IDL file.

Compare:
https://issues.apache.org/jira/browse/THRIFT-3089