Fix mode of files created in /tmp

[keithw]

umask should be user readable.

[anirudhSK]

I remember addressing this, but I don't remember which commit.

[ravinet]

We had fixed the files stored by recordshell to be user readable. Currently, the files created by replayshell (eg. error files, access logs) are in /tmp and are not user-readable.

[anirudhSK]

This needs to be fixed, because WebServer will be running with elevated privileges and hence could erase an old file belonging to the same user in /tmp/ (with very low probability).

On second thought, since these files are created using mkstemp, they are guaranteed to be unique (or return a non-zero value, if not).

[keithw]

It seems to be a POSIX requirement that mkstemp() files be mode 0600. I guess we can leave it.