Under restricted permissions (like inside a podman container) opening
"/proc/self/ns/net" fails with Permission denied. Consequently we cannot
create our bottom NMPNetns instance. That is mostly fine, however we
would log an error message with severity <error>.
Note that test "src/core/platform/tests/test-platform-general" asserts
that no <warn> and <error> messages get logged. Hence, the test will
fail.
That is undesirable. Downgrade the message to <debug> so that the test
passes. Also, it's not clear that this error message is useful here.
Being unable to open a netns fd is fine and not necessarily an error
condition.
We should always register the GArray stack with pthread
for cleanup the thread local storage. Do that first, before
creating the NMPNetns instance at the bottom of the stack.
