Fix for left over files and need to re-focus the window on interrupt

With this patch, in the same conditions i did https://github.com/musicbrainz/picard/pull/232#issuecomment-38776499 , i obtain:

```
18697 open("/tmp/picardk_0DAr", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18698 open("/tmp/picardap00j5", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18695 open("/tmp/picarduYHgHO", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18697 open("/tmp/picard_gM2Zw", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18696 open("/tmp/picardBBGKnv", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18698 open("/tmp/picardh3mAeV", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18695 open("/tmp/picardBO3GLG", O_RDWR|O_CREAT|O_EXCL|O_NOFOLLOW, 0600 <unfinished ...>
18682 rt_sigreturn(0xffffffff)          = -1 EINTR (Interrupted system call)
18682 unlink("/tmp/picardBO3GLG")       = 0
18682 unlink("/tmp/picardh3mAeV")       = 0
18682 unlink("/tmp/picardBBGKnv")       = 0
18682 unlink("/tmp/picard_gM2Zw")       = 0
18682 unlink("/tmp/picarduYHgHO")       = 0
18682 unlink("/tmp/picardap00j5")       = 0
18682 unlink("/tmp/picardk_0DAr")       = 0
```

No left over files.

It also fixes the need to re-focus after interrupt.