fix addressOverrideType enum generation

[killanch]

• This is to fix incorrect enum type generation for addressOverrideType attribute

Before:

addressOverrideType: new NUAttribute({
            localName: 'addressOverrideType',
            attributeType: NUAttribute.ATTR_TYPE_ENUM,
            description: `AddressOverride Type - either IPv4 or IPv6 or MACRO_GROUP. Possible values are IPV4, IPV6 and MACRO_GROUP.`,
            canOrder: true,
            canSearch: true,
            choices: [NUIPTypeEnum.IPV4, NUIPTypeEnum.IPV6, NUIPTypeEnum.MACRO_GROUP],
            userlabel: `Address Override Type`,
        }),

After:

addressOverrideType: new NUAttribute({
            localName: 'addressOverrideType',
            attributeType: NUAttribute.ATTR_TYPE_ENUM,
            description: `AddressOverride Type - either IPv4 or IPv6 or MACRO_GROUP. Possible values are IPV4, IPV6 and MACRO_GROUP.`,
            canOrder: true,
            canSearch: true,
            choices: [NUEgressAuditACLEntryTemplateAddressOverrideTypeEnum.IPV4,
                NUEgressAuditACLEntryTemplateAddressOverrideTypeEnum.IPV6,
                NUEgressAuditACLEntryTemplateAddressOverrideTypeEnum.MACRO_GROUP],
            userlabel: `Address Override Type`,
        }),

• If enum values for an attribute are part of generic enum values, then generic enum type is used for the attribute, https://github.com/nuagenetworks/monolithe/blob/master/monolithe/generators/lang/javascript/writers/apiversionwriter.py#L162
• In corner cases such as addressOverrideType, we cannot have IPType.MACRO_GROUP. For such attributes we specify an override in config.json such that generic type is not used