test fix: return 0 not num-of-bytes-written
test fix: return 0 not num-of-bytes-written

The api should return 0, not the number of bytes successfully written
(which is what snprintf directly returns).

Signed-off-by: Brenden Blanco <8e41c261aa8ddb01230a40c21c26a049c1f6d041@gmail.com>

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