We currently re-run all the grub setup in 99-fix-grub-timeout which
shouldn't really be necessary (actually a little problematic; although
this is dib's fault, see Ibaaa81124098f3c6febe48e455d3e1cd0a5f1761)
Use the new timeout flag to set this in the bootloader element
directly.
I think it is also an advantage that if you build a testing image with
./tools/build_image.sh this is configurable now ... having to fiddle
the bootloader for debugging is something that happens more than you'd
like.
This is supported since dib 1.26.0
Change-Id: Iafc660a9a8c072af6bf1fd5e51c419abccef4d54