nvlist_take_number
flags = nvlist_take_number(nvl, "chanflags");
pp->p_proto = (int)nvlist_take_number(nvl, "proto");
ATF_REQUIRE_EQ(nvlist_take_number(nvl, testkey), testval);
ATF_REQUIRE_EQ(nvlist_take_number(nvl, testkey), testval);
uint64_t nvlist_take_number(nvlist_t *nvl, const char *name);