runtime: Fix exported edges not reset on new graph
runtime: Fix exported edges not reset on new graph

Caused microflo-core FBP spec tests to fail when running more than
one suite

rraallvv/microflo,microflo/microflo,microflo/microflo,microflo/microflo,microflo/microflo,rraallvv/microflo,rraallvv/microflo,microflo/microflo,microflo/microflo,rraallvv/microflo