Bug#1119959: the problem is that remove grub2-common remove files just installed by grub-common

[Eric Valette]

as the file in grub2-common during the transition from 2.12 to 2.14 
migrated from grub-common to  grub2-common, when removing files it 
remove the grub-common just installed files.

If you reainstall manually grub-common and do apt -f install you manage 
to downgrade.

However there is a logical bug in installation as grub2-common should be 
removed/downgraded before grub-common is installed...

-- 
Eric Valette