Add check of result chmod() in RAND_file_name(...)

[nv-dmd]

OpenSSL 3.0.14

In the function RAND_file_name(), chmod(file, 0600) is executed on line 249.
But the result of the chmod(...) function execution is not checked.
Maybe it is worth checking the result, because chmod(...) should restrict permissions and its successful execution seems important?

[paulidale]

Yes, it is import but only if you are running VMS. On Unix like systems, the file is created with mode 0600 on line 210 making this redundant.

This chmod should be conditioned as VMS only and the return value should be checked.
It's also a race condition waiting to happen.

Fortunately, OpenSSL doesn't attribute any entropy to rand-files, so this isn't going to compromise the RAND subsystem.