Fix stacktrace when register/unregister a probe not defined in conf
Fix stacktrace when register/unregister a probe not defined in conf

Change-Id: Ib3df354f7c74c3091bd8116e0eb580ce0bd72bfd

redhat-cip/skydive,skydive-project/skydive,safchain/skydive,skydive-project/skydive,safchain/skydive,safchain/skydive,safchain/skydive,safchain/skydive,lebauce/skydive,lebauce/skydive,lebauce/skydive,safchain/skydive,lebauce/skydive,skydive-project/skydive,safchain/skydive,lebauce/skydive,skydive-project/skydive,redhat-cip/skydive,lebauce/skydive,redhat-cip/skydive,lebauce/skydive,skydive-project/skydive,safchain/skydive,skydive-project/skydive,lebauce/skydive,skydive-project/skydive