Fix the fuzz bug

We have a bug in the `run_task` script where by in processing the `fuzz`
crate we _break_ instead of continuing. This means any crate listed
after `fuzz` in the `CRATES` env var will be skipped. However we don't
want to bother with the `test_vars.sh` script in `fuzz`, so continue to
handle the `fuzz` crate inline in `build_and_test` but call `continue`.

While we are at it call `cargo test` for good measure.

ci/run_task.sh

@@ -111,12 +111,16 @@ build_and_test() {
     for crate in "${CRATES[@]}"; do
         local test_vars_script="$REPO_DIR/$crate/contrib/test_vars.sh"
 
-        # Building the fuzz crate is more-or-less just a sanity check.
+        # Building/testing the fuzz crate is more-or-less just a sanity check.
+        #
+        # Do it here instead of calling down to `do_test` so we don't have to
+        # worry about `contrib/test_vars.sh` in the `fuzz` crates.
         if [ "$crate" = "fuzz" ]; then
             pushd "$REPO_DIR/$crate" > /dev/null
             cargo --locked build
+            cargo --locked test
             popd > /dev/null
-            break
+            continue
         fi
 
         verbose_say "Sourcing $test_vars_script"