mdbx: fix resource-leak in mdbx_env_open_ex() in case of error (coverity).
mdbx: fix resource-leak in mdbx_env_open_ex() in case of error (coverity).

Change-Id: I9e808e2de4a64d05205a79c9d90feacc87ec930d

leo-yuriev/libfpta,leo-yuriev/libfpta