Currently, the etcd client is initialized with a context that gets
immediately closed once the initialization completed, in turn causing
the etcd client to be stopped. Let's fix this by using the parent
context, which gets closed only once the migration terminates.

Additionally, let's explicitly wait for the client to connect, so
that we can return an explicit error in case of problems, rather
than failing at a later stage.

Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>

The retrieval of node information is not required during the migration
of identities, and the current implementation leads to a panic given
that the local node store is not initialized. Hence, let's just drop
it altogether.

Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>

shutdowner.Shutdown takes a variadic number of parameters, hence let's
just omit it.

Signed-off-by: Marco Iorio <marco.iorio@isovalent.com>