Set the default editor inside the chroot
Set the default editor inside the chroot

Allows the chroot builder to set the default editor to be used in the
chroot.

Vim is used as the default choice.

Signed-off-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

onponomarev/ganeti,bitemyapp/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,leshchevds/ganeti,apyrgio/snf-ganeti,dimara/ganeti,mbakke/ganeti,mbakke/ganeti,apyrgio/ganeti,ganeti/ganeti,ganeti/ganeti,andir/ganeti,grnet/snf-ganeti,leshchevds/ganeti,apyrgio/ganeti,ganeti/ganeti,yiannist/ganeti,andir/ganeti,dimara/ganeti,grnet/snf-ganeti,mbakke/ganeti,bitemyapp/ganeti,yiannist/ganeti,apyrgio/snf-ganeti,yiannist/ganeti,leshchevds/ganeti,onponomarev/ganeti,ganeti-github-testing/ganeti-test-1