Cloudooo: remove ffmpeg

Currently cloudooo does not compile with gcc 6.3 ( default gcc from current debian stable ) because of ffmpeg component:

```
    [CC] nestegg/halloc/src/halloc.c.o
In file included from nestegg/halloc/src/halloc.c:19:0:
nestegg/halloc/src/align.h:33:25: error: conflicting types for 'max_align_t'
 typedef union max_align max_align_t;
                         ^~~~~~~~~~~
In file included from nestegg/halloc/src/../halloc.h:18:0,
                 from nestegg/halloc/src/halloc.c:18:
/usr/lib/gcc/x86_64-linux-gnu/6/include/stddef.h:429:3: note: previous declaration of 'max_align_t' was here
 } max_align_t;
   ^~~~~~~~~~~
Makefile:104: recipe for target 'nestegg/halloc/src/halloc.c.o' failed
```

Because we don't use ffmpeg in cloudooo, I'm just temporarily removing it .

/cc @rafael @kazuhiko @gabriel @vpelletier

/reviewed-on nexedi/slapos!264

stack/cloudooo.cfg

@@ -8,7 +8,6 @@ extends =
   ../component/dash/buildout.cfg
   ../component/dbus/buildout.cfg
   ../component/dcron/buildout.cfg
-  ../component/ffmpeg/buildout.cfg
   ../component/file/buildout.cfg
   ../component/fonts/buildout.cfg
   ../component/git/buildout.cfg
@@ -69,7 +68,6 @@ parts =
   wkhtmltopdf
   file
   poppler
-  ffmpeg
 
   rdiff-backup
   apache