tools/capable: fix compilation error
tools/capable: fix compilation error

9d7feeed87c5 ("tools: add option --unique to capable.py") introduced a
compilation error when the --unique flag is passed.

Signed-off-by: Mauricio Vásquez <95f407c1ffa7689a0a3f2f21b1bf582fe8359351@kinvolk.io>

tuxology/bcc,brendangregg/bcc,iovisor/bcc,tuxology/bcc,tuxology/bcc,brendangregg/bcc,iovisor/bcc,tuxology/bcc,iovisor/bcc,brendangregg/bcc,iovisor/bcc,brendangregg/bcc,tuxology/bcc,brendangregg/bcc,iovisor/bcc