Fix perf_reader log message format string warning
Fix perf_reader log message format string warning

shodoco/bcc,romain-intel/bcc,iovisor/bcc,mcaleavya/bcc,iovisor/bcc,tuxology/bcc,romain-intel/bcc,tuxology/bcc,shodoco/bcc,brendangregg/bcc,brendangregg/bcc,tuxology/bcc,tuxology/bcc,tuxology/bcc,romain-intel/bcc,mcaleavya/bcc,mcaleavya/bcc,shodoco/bcc,iovisor/bcc,shodoco/bcc,brendangregg/bcc,romain-intel/bcc,mcaleavya/bcc,iovisor/bcc,brendangregg/bcc,iovisor/bcc,romain-intel/bcc,shodoco/bcc,brendangregg/bcc,mcaleavya/bcc