stream: fix potential memory loss on error

Coverity 1139543.

If StreamTcpPseudoPacket would be called with len == 0, the packet
it acquired before checking the len value would be lost.
conf: fix potential use-after-free on error

Coverity 1139544

If strdup would fail, 'node' was freed but it wasn't set to NULL. The
code then returned node. The caller would not detect there was an error
and use the freed pointer.