selftests/vsock: speed up tests by reducing the QEMU pidfile timeout

selftests/vsock: speed up tests by reducing the QEMU pidfile timeout

Reduce the time waiting for the QEMU pidfile from three minutes to five
seconds. The three minute time window was chosen to make sure QEMU had
enough time to fully boot up. This, however, is an unreasonably long
delay for QEMU to write the pidfile, which happens earlier when the QEMU
process starts (not after VM boot). The three minute delay becomes
noticeably wasteful in future tests that expect QEMU to fail and wait a
full three minutes for a pidfile that will never exist.

Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Bobby Eshleman <bobbyeshleman@meta.com>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://patch.msgid.link/20251108-vsock-selftests-fixes-and-improvements-v4-6-d5e8d6c87289@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>