Wait for snapd to seed before installing snaps
Currently dist-git tests fail with the following error:
+ snap list
No snaps are installed yet. Try 'snap install hello-world'.
+ snap install test-snapd-tools
error: too early for operation, device not yet seeded or device model not acknowledged
It looks like the test ought to wait for snapd to seed to start
accepting installation requests.
Signed-off-by: Zygmunt Krynicki <me@zygoon.pl>