lib/model: Correct virtual mtime handling (fixes #3516)
lib/model: Correct virtual mtime handling (fixes #3516)

We previously set the mtime on the temp file, and then renamed it to the
real path. Unfortunately that means we'd save the real timestamp under
the under the temp name ".syncthing.foo.tmp" when the actual file that
we will look up on the next scan is "foo". This moves the Chtimes later,
ensuring that it gets recorded correctly under the right name.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/3519

rumpelsepp/syncthing,jryans/syncthing,nrm21/syncthing,wweich/syncthing,brgmnn/syncthing,kluppy/syncthing,nrm21/syncthing,kamadak/syncthing,brgmnn/syncthing,wweich/syncthing,jryans/syncthing,AudriusButkevicius/syncthing,brgmnn/syncthing,plouj/syncthing,lkwg82/syncthing,le9i0nx/syncthing,imsodin/syncthing,cherylquirion/syncthing,Kudalufi/syncthing,rumpelsepp/syncthing,imsodin/syncthing,nrm21/syncthing,kluppy/syncthing,kluppy/syncthing,ProactiveServices/syncthing,xduugu/syncthing,kamadak/syncthing,syncthing/syncthing,wweich/syncthing,nrm21/syncthing,syncthing/syncthing,kamadak/syncthing,jryans/syncthing,letiemble/syncthing,uok/syncthing,ProactiveServices/syncthing,imsodin/syncthing,Kudalufi/syncthing,AudriusButkevicius/syncthing,uok/syncthing,xduugu/syncthing,imsodin/syncthing,syncthing/syncthing,rumpelsepp/syncthing,Kudalufi/syncthing,ProactiveServices/syncthing,syncthing/syncthing,cherylquirion/syncthing,syncthing/syncthing,lkwg82/syncthing,plouj/syncthing,letiemble/syncthing,letiemble/syncthing,cherylquirion/syncthing,jryans/syncthing,lkwg82/syncthing,plouj/syncthing,le9i0nx/syncthing,syncthing/syncthing,plouj/syncthing,le9i0nx/syncthing,brgmnn/syncthing,AudriusButkevicius/syncthing,imsodin/syncthing,kamadak/syncthing,uok/syncthing,wweich/syncthing,AudriusButkevicius/syncthing,lkwg82/syncthing,letiemble/syncthing,rumpelsepp/syncthing,xduugu/syncthing,kluppy/syncthing,ProactiveServices/syncthing,cherylquirion/syncthing,Kudalufi/syncthing,uok/syncthing,le9i0nx/syncthing,xduugu/syncthing