attr: Warn application if nla_parse() observes same attribute multiple times
attr: Warn application if nla_parse() observes same attribute multiple times

Use a debugging message to warn applications if an attribute is
found multiple times in the same message. It is perfectly valid
to rely on this behaviour but it is likely to indicate a bug.

Signed-off-by: Thomas Graf <17c2d8920621522552b392f72d8fdb4d1e866b44@suug.ch>

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