Calendar component doesn't respect dateFormat config value

[dmitryrogov]

Config ('primevue/config') contains dateFormat options to represent default date format, but Calendar component override this value by its own default value in props:

dateFormat: {
    type: String,
    default: 'mm/dd/yy'
}

and then it leads to wrong behavior in computed property:

datePattern() {
    return this.dateFormat || this.$primevue.config.locale.dateFormat;
}

primevue version in 2.3.0