_zg_err_errno() should save the current errno value before calling any
libc functions because they could change it. Failing to do so, may result
in _zg_err_errno() displaying an incorrect error message.
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>