Protect Button saves wrong protection names if a locale is a default in a tree but not the master default

Protect Button saves wrong protection names if a locale is a default in a tree but not the master default.

Steps to reproduce

1.  Create a master tree with en_US as default, de_CH as second and en_GB as third locale
2.  Create a slave tree with en_US as masterDefaultLocale and en_GB as fallback for this tree.
3. Go to the page protect button and protect the en_GB version of a property.

Expected results

Because en_GB is not the master default locale the en_GB should be saved as suffix

Actual results

It will create a <propertyName> in the protectedFields property without language suffix.

Development notes

The issue is in the Button:

https://git.magnolia-cms.com/projects/ADDON/repos/live-copy/browse/src/main/java/info/magnolia/livecopy/app/ui/layout/field/ProtectFieldButton.java

It uses an own implementation of isDefaultLocale at line 102. Instead you should use the isDefaultLocale method from https://git.magnolia-cms.com/projects/ADDON/repos/live-copy/browse/src/main/java/info/magnolia/livecopy/i18n/LiveCopyMultiSiteI18nAuthoringSupport.java