tests: add recursive classic confinement call test
This test validates that a snap using classic confinement can call into the snap itself. We discovered several bugs related to this behavior so the test will help to ensure this does not regress anymore.
Signed-off-by: Zygmunt Krynicki <email address hidden>
We need to special case the env handling for snapd re-execing from 2.21. In this version of snap/snapd we did set SNAP_REEXEC=0 when we re-execed.
In this case we need to unset the reExecKey to ensure that subsequent run of snap/snapd (e.g. when using classic confinement) will *not* prevented from re-execing.