dlfcn: Fix dladdr return value

Noticed a minor bug in the OSv dlfcn implementation.
According to the linux man pages, dladdr returns non-zero on success
and zero on error -> http://linux.die.net/man/3/dladdr

Signed-off-by: Dinakar Guniguntala <dino@linux.vnet.ibm.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>