fix #1612 contact us button after repeated login failures

fix #1612 contact us button after repeated login failures

Implement suggestions from https://github.com/wordpress-mobile/WordPress-Android/pull/1686 (buttons width and lost password button).
only `showError(int messageId)` is called directly and it checks if activity is added (https://github.com/wordpress-mobile/WordPress-Android/blob/issue/1612-contact-us-button-after-repeated-login-failures/WordPress/src/main/java/org/wordpress/android/ui/accounts/NewAccountAbstractPageFragment.java#L120). I moved the check down to `showError(String message)` in 57d694c