Bug 5883 - no constructor for indentityref in union

Bug 5883 - no constructor for indentityref in union

The generated java code for union with identityref doens't include a
constructor for identityref.

module union-with-identityref {
    yang-version 1;
    namespace "urn:opendaylight:yang:union:test";
    prefix "uniontest";

    description "test union with identityref";

    revision "2016-05-09";

    identity ident-base;
    identity ident-one {
        base ident-base;
    }
    identity ident-two {
        base ident-base;
    }

    typedef union-type {
        type union {
            type uint8;
            type identityref {
                base ident-base;
            }
        }
    }
}

generated java code:
public class UnionType
 implements Serializable {
    private static final long serialVersionUID = 4724108168179933454L;
    private final java.lang.Short _uint8;
    private final char[] _value;

    public UnionType(java.lang.Short _uint8) {
        super();
        this._uint8 = _uint8;
        this._value = _uint8.toString().toCharArray();
    }

Change-Id: Idf8f7df54afd0934e47b19c131ea41d046a7b5df
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>