rbtree: Fix rb_insert
rbtree: Fix rb_insert

Insertion code would check for pointer equality whereas it
must check for item equality using the supplied comparator.

Signed-off-by: Michael Foukarakis <5d793639974103e3c941c2daad1930268b97c02d@bmw.de>

mfukar/libhelper,mfukar/libhelper