Add missing expectations in common actions

We weren't checking that the request caused by clicking on the "Send
instructions" button had finished before continuing with the test.
Perhaps that's why this test has recently failed on our CI:

```
3) Emails Reset password
     Failure/Error: email = open_last_email

     RuntimeError:
       No email has been sent!
```

We're also adding an expectation to the `login_as_manager` method and
the methods to submit proposal and investment forms to make sure that,
when these method finish, the request finishes as well.

spec/support/common_actions/maps.rb

@@ -7,9 +7,12 @@ module Maps
   def submit_proposal_form
     check :proposal_terms_of_service
     click_button "Create proposal"
+    expect(page).to have_content "Proposal created successfully."
 
     if page.has_content?("Not now, go to my proposal")
       click_link "Not now, go to my proposal"
+
+      expect(page).not_to have_link "Not now, go to my proposal"
     end
   end
 
@@ -22,6 +25,7 @@ module Maps
   def submit_budget_investment_form
     check :budget_investment_terms_of_service
     click_button "Create Investment"
+    expect(page).to have_content "Budget Investment created successfully"
   end
 
   def set_arguments(arguments, mappable, mappable_path_arguments)

spec/support/common_actions/users.rb

@@ -49,6 +49,8 @@ module Users
   def login_as_manager(manager = create(:manager))
     login_as(manager.user)
     visit management_sign_in_path
+
+    expect(page).to have_content "Management"
   end
 
   def login_managed_user(user)
@@ -74,6 +76,9 @@ module Users
 
     fill_in "user_email", with: "manuela@consul.dev"
     click_button "Send instructions"
+
+    expect(page).to have_content "If your email address is in our database, in a few minutes " \
+                                 "you will receive a link to use to reset your password."
   end
 
   def expect_to_be_signed_in