Use create_hook helper

Use extracted create_hook helper in tests for:

- exec
- hooks
- rehash
- version-name
- version-origin
- which

test/version-origin.bats

@@ -32,12 +32,9 @@ setup() {
 }
 
 @test "reports from hook" {
-  mkdir -p "${RBENV_ROOT}/rbenv.d/version-origin"
-  cat > "${RBENV_ROOT}/rbenv.d/version-origin/test.bash" <<HOOK
-RBENV_VERSION_ORIGIN=plugin
-HOOK
+  create_hook version-origin test.bash <<<"RBENV_VERSION_ORIGIN=plugin"
 
-  RBENV_VERSION=1 RBENV_HOOK_PATH="${RBENV_ROOT}/rbenv.d" run rbenv-version-origin
+  RBENV_VERSION=1 run rbenv-version-origin
   assert_success "plugin"
 }