Refactor circuit_predict_and_launch_new

changes/ticket18873

src/or/circuitbuild.c

src/or/circuitbuild.h

src/or/circuituse.c

src/or/circuituse.h

src/or/nodelist.c

src/or/nodelist.h

src/test/include.am

src/test/test.c

src/test/test.h

src/test/test_circuituse.c