route: fix return value of nl_rtgen_request()
route: fix return value of nl_rtgen_request()

According to documentation, nl_rtgen_request() returns 0 on success,
but before it returned the number of bytes sent.

Signed-off-by: Thomas Haller <16e26612e4159990a6b3691e92592e691ff74132@redhat.com>

thom311/libnl,mshirley/libnl,congwang/libnl,cyclops8456/libnl3,baloo/libnl,greearb/libnl-ct,greearb/libnl-ct,honsys/libnl,houstar/libnl,HolyShitMan/libnl-1,vyos/libnl3,vyos/libnl3,tgraf/libnl,honsys/libnl,tgraf/libnl,thom311/libnl,houstar/libnl,thom311/libnl,tklauser/libnl,dsahern/libnl,UnicronNL/libnl3,tklauser/libnl,UnicronNL/libnl3,cfriedt/libnl,cyclops8456/libnl3,cfriedt/libnl,congwang/libnl,kolyshkin/libnl,mshirley/libnl,honsys/libnl,honsys/libnl,HolyShitMan/libnl-1,tgraf/libnl,houstar/libnl,mshirley/libnl,HolyShitMan/libnl-1,dsahern/libnl,claudelee/libnl,kolyshkin/libnl,kolyshkin/libnl,tgraf/libnl,baloo/libnl,dsahern/libnl,cfriedt/libnl,cfriedt/libnl,houstar/libnl,vyos/libnl3,cyclops8456/libnl3,claudelee/libnl,congwang/libnl,kolyshkin/libnl,cyclops8456/libnl3,congwang/libnl,dsahern/libnl,greearb/libnl-ct,UnicronNL/libnl3,mshirley/libnl,tklauser/libnl,baloo/libnl,UnicronNL/libnl3,claudelee/libnl,HolyShitMan/libnl-1,claudelee/libnl,vyos/libnl3,tklauser/libnl,baloo/libnl