MFstable/10 r301789:

MFC r299491:
r299491 (by cem):

route6d(8): Fix potential double-free

In the case that the subsequent sysctl(3) call failed, 'buf' could be free(3)ed
repeatedly. It isn't clear to me that that case is possible, but be clear and
do the right thing in case it is.

CID: 272537