mktemp: Don't panic when getrandom failed

[oech3]

Closes #11153

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/follow-name (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tail/symlink (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/tty/tty-eof (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/pr/bounded-memory (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/printf/printf-surprise is now passing!
Congrats! The gnu test tests/tail/tail-n0f is now passing!

[sylvestre]

can it be triggered?

[oech3]

Not sure. happen after boot process with 0 entropy pool without strace...?

[oech3]

It seems this is making a sense at old version of kernel.