Add missing expectations in mappable tests

After clicking the "Save changes" button, we were sometimes checking
expectations that were already true before clicking the button, so it
was possible that the request generated by that button didn't finish
before the test did.

So now we're checking that the button is no longer present, which is
only true after the request has finished.

spec/shared/system/mappable.rb

@@ -198,6 +198,8 @@ shared_examples "mappable" do |mappable_factory_name, mappable_association_name,
       visit send(mappable_edit_path, id: mappable.id)
       find(".map-location").click
       click_button "Save changes"
+
+      expect(page).not_to have_button "Save changes"
       mappable.reload
 
       expect(page).to have_css(".map-location")
@@ -211,6 +213,8 @@ shared_examples "mappable" do |mappable_factory_name, mappable_association_name,
       visit send(mappable_edit_path, id: mappable.id)
       fill_in "#{mappable_factory_name.camelize} title", with: "New title"
       click_button "Save changes"
+
+      expect(page).not_to have_button "Save changes"
       mappable.reload
 
       expect(page).to have_css(".map-location")
@@ -225,7 +229,8 @@ shared_examples "mappable" do |mappable_factory_name, mappable_association_name,
       click_button "Remove map marker"
       click_button "Save changes"
 
-      expect(page).not_to have_css(".map-location")
+      expect(page).not_to have_button "Save changes"
+      expect(page).not_to have_css ".map-location"
     end
 
     scenario "Can not display map on #{mappable_factory_name} edit when feature.map is disabled" do
@@ -236,7 +241,8 @@ shared_examples "mappable" do |mappable_factory_name, mappable_association_name,
       fill_in "#{mappable_factory_name.camelize} title", with: "New title"
       click_button "Save changes"
 
-      expect(page).not_to have_css(".map-location")
+      expect(page).not_to have_button "Save changes"
+      expect(page).not_to have_css ".map-location"
     end
 
     scenario "No need to skip map on update" do
@@ -246,6 +252,7 @@ shared_examples "mappable" do |mappable_factory_name, mappable_association_name,
       click_button "Remove map marker"
       click_button "Save changes"
 
+      expect(page).not_to have_button "Save changes"
       expect(page).not_to have_content "Map location can't be blank"
     end
   end