notmuch: Fix auto_tag=yes for modify-labels* and quasi-delete

When 'auto_tag' was 'yes', <modify-labels>* and <quasi-delete> still only
applied to the currently-selected message. Now they apply to all tagged
messages, as they should.



Four cases tested with the patch:
1) auto_tag=yes, tag two message, press ` - now both messages are labelled
2) auto_tag=yes, tag two message, press ;` - now both messages are labelled
3) auto_tag=no, tag two message, press ` - now only selected message is labelled
4) auto_tag=no, tag two message, press ;` - now both messages are labelled