test: fix thread race in process_title_threadsafe
test: fix thread race in process_title_threadsafe

Libuv calls uv__process_title_cleanup() on shutdown, which raced with
one of the threads from the test that calls uv_get_process_title() in
an infinite loop. Change the test to properly shut down the thread
before exiting.

PR-URL: https://github.com/libuv/libuv/pull/2946
Refs: https://github.com/libuv/libuv/pull/2853#issuecomment-665259082
Reviewed-By: Colin Ihrig <838f779c91673db29b8572ea3f54d191d3878ae2@gmail.com>
Reviewed-By: Jameson Nash <99e7f19e9f64df56d4e81dc00b8566e722cdd766@gmail.com>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso