Make AFont_getLocale work

There are multiple problems here:
- Java Font.equals and hashCode doesn't look at locale list. Due to this
issue, the CTS tests have been passing unexpectedly.
- The null pointer check in the AFont_getLoacle was inversed. Should
return only when it is non-null.
- Looks like we cannot get the parent's attribute which always returns
null. Instead, read the "lang" attribute when we read the family tag.

Bug: 139201432
Test: atest NativeSystemFontTest
Test: atest TypefaceEqualsTest
Change-Id: I0514847bbf46a73358afab374ccfce2db09b2ec0