Bugfix release:
- many: add wait command and seeded target (2
- snapd.core-fixup.sh: add workaround for corrupted uboot.env
- boot: clear "snap_mode" when needed
- cmd/libsnap: fix compile error on more restrictive gcc
- tests: cherry-pick commits to move spread to google backend
- spread.yaml: add cosmic (18.10) to autopkgtest/qemu
- userd: set up journal logging streams for autostarted apps