add: Avoid unncessarily converting a newly unlocked file to be stored
in git when it is not modified, even when annex.largefiles does not
match it.
This fixes a reversion in version 10.20220222, where git-annex unlock
followed by git-annex add, followed by git commit file could result in
git thinking the file was modified after the commit.
I do have half a mind to remove the withUnmodifiedUnlockedPointers part
of git-annex add. It seems weird, despite that old bug report arguing
a case of consistency that it ought to behave that way. When git-annex
add surpises me, it seems likely it's wrong.. But for now, this is the
smallest possible fix.
Sponsored-by: Dartmouth College's Datalad project
