ustat: added basic race condition protection (#2103)
ustat: added basic race condition protection (#2103)

added basic race condition protection for ustat.py
brendangregg/bcc,brendangregg/bcc,tuxology/bcc,tuxology/bcc,mcaleavya/bcc,tuxology/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc,tuxology/bcc,brendangregg/bcc,iovisor/bcc,mcaleavya/bcc,mcaleavya/bcc,mcaleavya/bcc,mcaleavya/bcc,tuxology/bcc,iovisor/bcc,iovisor/bcc,brendangregg/bcc