libuuid: clear uuidd cache on fork()

libuuid: clear uuidd cache on fork()

After fork() the memory of the calling thread is preserved into the new
process. This also includes TLS.
Make sure to reset the cache after a fork to avoid reuse of cached
values.

Only the TLS of the thread calling fork() is relevant as that is the
only thread that gets forked.
New threads will received newly initialized TLS.

Fixes https://github.com/util-linux/util-linux/issues/3009
Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>
Gbp-Pq: Topic upstream-master
Gbp-Pq: Name libuuid-clear-uuidd-cache-on-fork.patch