fix(shares): Fix infinite loop when all shares are invalid

[come-nc]

Summary

I do not know if there are other ways to trigger the issue than this one:

1. Use LDAP
2. Enable option to mark remnants as disabled
3. occ config:app:set files_sharing hide_disabled_user_shares --value yes
4. With an LDAP user, share something
5. Change the LDAP filter to exclude this user
6. occ ldap:check-user <myuser> (turns the user into a remnant)
7. occ ldap:show-remnants -> The command never finish

This is because in commit 8c9aa9a , I made it possible for method checkShare to throw ShareNotFound without deleting the share.
I’m now passing the added count as a reference to the method so that it get decremented if needed only.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

[come-nc]

/backport to stable32

[come-nc]

/backport to stable31

[come-nc]

/backport to stable30

[come-nc]

Note: all remnant accounts are listed with "N" in the "Sharer" column, even if they have (hidden) shares.

This is because remnants are seen as disabled and their shares deactivated. We should hide the column or fix the value in it.