e2fsprogs: prevent undesired cleanup with a usr merged target

The following commit prevents the e2fsprogs package from inadvertently
removing its own binaries when a target includes BusyBox and is
targeting a usr-merged environment.

While an action has been added to cleanup BusyBox-provided (if any)
ext2-related tools when including e2fsprogs, the action will delete
desired e2fsprogs binaries in an already prepared usr-merged target.
Adjusting the cleanup to occur before installing e2fsprogs binaries so
that if a usr-merged target exists, it will first delete the previous
binaries (if any) followed by installing new binaries.

Signed-off-by: James Knight <james.knight@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>