Divert flash-kernel to allow all packages to configure.
In a foreign chroot, flash-kernel do not work properly and block
itself and initramfs-tools pakcages from configuring.  This in turn
can block other packages from being installed.  Avoid the problem by
diverting the flash-kernel binary away while configuring packages.
Merge pull request #24 from petterreinholdtsen/divert-flash-kernel

Divert flash-kernel to allow all packages to configure.