Remove grub2 files from ostree-boot package

Endless doesn't use the full GRUB integration (etc/grub.d/15_ostree),
but instead we only use the Boot Loader Spec (BLS) configuration from
GRUB to show new ostree entries.

Rebase 2019.3 (T27607): replaced 4705bb8 "Restore ostree-boot files to main ostree package"

Debian doesn't install the ostree-boot package since they don't have a
way to confirm it works, but we install those pieces as part of the main
ostree package. The only exception is the full GRUB integration
(etc/grub.d/15_ostree), where we only use the Boot Loader Spec (BLS)
configuration from GRUB to show new ostree entries.

https://phabricator.endlessm.com/T17204

Rebase 2018.6 (T23138): Move the new systemd service
  lib/systemd/system/ostree-finalize-staged.service from ostree-boot to
  ostree
Rebase 2019.1 (T25195): Move ostree-finalize-staged.path from
  ostree-boot to ostree
Rebase 2019.3 (T27607): Re-integrate non-grub parts with ostree-boot
  package which is now built in debian.

debian/ostree-boot.install

@@ -1,5 +1,4 @@
 etc/dracut.conf.d/ostree.conf
-etc/grub.d/15_ostree
 lib/systemd/system-generators/ostree-system-generator
 lib/systemd/system/ostree-finalize-staged.path
 lib/systemd/system/ostree-finalize-staged.service
@@ -9,4 +8,3 @@ usr/lib/dracut/modules.d/98ostree
 usr/lib/ostree/ostree-prepare-root
 usr/lib/ostree/ostree-remount
 usr/lib/tmpfiles.d/ostree-tmpfiles.conf
-usr/libexec/libostree/grub2-15_ostree

debian/rules

@@ -66,6 +66,9 @@ override_dh_install:
 	rm -f debian/tmp/usr/lib/*/*.la
 	rm -f debian/tmp/usr/libexec/installed-tests/libostree/*.la
 	:
+	rm -f debian/tmp/etc/grub.d/15_ostree
+	rm -f debian/tmp/usr/libexec/libostree/grub2-15_ostree
+	:
 	dh_install
 
 override_dh_missing: