Tweaks import url step so it doesn't override existing steps

import-flow-back-button.patch

diff --git a/client/lib/signup/step-actions.js b/client/lib/signup/step-actions.js
index 973d8a89ad..40eb0967ff 100644
--- a/client/lib/signup/step-actions.js
+++ b/client/lib/signup/step-actions.js
@@ -637,15 +637,18 @@ export function isPlanFulfilled( stepName, defaultDependencies, nextProps ) {
 }
 
 export function isSiteTypeFulfilled( stepName, defaultDependencies, nextProps ) {
-	let siteType, siteTypeValue;
-
-	if ( nextProps.flowName === 'import' ) {
-		siteType = siteTypeValue = 'import';
-	} else {
-		siteType = get( nextProps, [ 'initialContext', 'query', 'site_type' ], null );
-		siteTypeValue = getSiteTypePropertyValue( 'slug', siteType, 'slug' );
+	if ( isEmpty( nextProps.initialContext && nextProps.initialContext.query ) ) {
+		return;
 	}
 
+	const {
+		initialContext: {
+			query: { site_type: siteType },
+		},
+	} = nextProps;
+
+	const siteTypeValue = getSiteTypePropertyValue( 'slug', siteType, 'slug' );
+
 	let fulfilledDependencies = [];
 
 	if ( siteTypeValue ) {
diff --git a/client/signup/steps/import-url/index.jsx b/client/signup/steps/import-url/index.jsx
index afd43a82a5..cc823896f4 100644
--- a/client/signup/steps/import-url/index.jsx
+++ b/client/signup/steps/import-url/index.jsx
@@ -31,6 +31,7 @@ import {
 	SITE_IMPORTER_ERR_INVALID_URL,
 } from 'lib/importers/constants';
 import Notice from 'components/notice';
+import { saveSignupStep } from 'state/signup/progress/actions';
 
 /**
  * Style dependencies
@@ -50,6 +51,7 @@ class ImportURLStepComponent extends Component {
 	};
 
 	componentDidMount() {
+		this.props.saveSignupStep( { stepName: this.props.stepName } );
 		this.setInputValueFromProps();
 		this.focusInput();
 	}
@@ -289,6 +291,7 @@ export default flow(
 			isLoading: isUrlInputDisabled( state ),
 		} ),
 		{
+			saveSignupStep,
 			setNuxUrlInputValue,
 			recordTracksEvent,
 			submitImportUrlStep,