Subsequent calls to nm_strerror_native() overwrite the previous
buffer. That is potentially dangerious. At least functions in
shared/nm-utils (which are lower-layer utilities) should not do
that and instead use a stack-local buffer. That is because these
functions should not make assumptions about the way they are called.

On the other end, nmcli passing the return-value of nm_strerror_native()
to g_print() is clearly OK because the higher layers are in control of
when the call nm_strerror_native() -- by relying that lower layers don't
interfere.