title: First name, last name and email address leak in forms randomly
body: <p>we have implemented django-allauth into our web app and we are facing random leaks.</p>
  
  <p>When a new user enters signup page, sometimes <strong>user sees first name, last name and email address of lastly logged user prefilled in signup form</strong>. This occurs really randomly, just sometimes. This also happens in profile edit form, which is just simple django form taking instance of user from self.request.user in CBV (FormView) like this:</p>
  
  <pre><code>def get_form_kwargs(self):
      kwargs = super(ProfileView, self).get_form_kwargs()
      kwargs.update({
          'instance': self.request.user
      })
      return kwargs
  </code></pre>
  
  <p>We are using basic default setup of allauth from the website installation instructions. We use it as for now just for email registration and login. </p>
  
  <p>allauth settings.py (all other settings we have the same like in instructions eg. installed apps, middlewares etc):</p>
  
  <pre><code># DJANGO-ALLAUTH
  ACCOUNT_ADAPTER = 'users.adapter.AccountAdapter'
  LOGIN_URL = '/accounts/login/'
  LOGIN_REDIRECT_URL = 'bookings:booking_add'
  ACCOUNT_FORMS = {'signup': 'users.forms.SignupForm', }
  ACCOUNT_AUTHENTICATION_METHOD = 'email'
  ACCOUNT_EMAIL_REQUIRED = True
  ACCOUNT_EMAIL_VERIFICATION = 'none'
  ACCOUNT_USERNAME_REQUIRED = False
  ACCOUNT_CONFIRM_EMAIL_ON_GET = True
  ACCOUNT_LOGOUT_ON_GET = True
  SOCIALACCOUNT_EMAIL_VERIFICATION = 'none'
  ACCOUNT_EMAIL_SUBJECT_PREFIX = ""
  ACCOUNT_LOGIN_ON_EMAIL_CONFIRMATION = True
  
  AUTH_USER_MODEL = 'users.User'
  
  AUTHENTICATION_BACKENDS = (
      'django.contrib.auth.backends.ModelBackend',
      'allauth.account.auth_backends.AuthenticationBackend',
  )
  </code></pre>
  
  <p>as <strong>signupView</strong> we use default one, but we also tried adding never_cache decorator (did not help):</p>
  
  <pre><code>class SignupView(AllauthSignupView):
      template_name = 'account/signup.html'
  
  signup = never_cache(SignupView.as_view())
  </code></pre>
  
  <p><strong>SignupForm</strong>, overriding default one:</p>
  
  <pre><code>class SignupForm(AllauthSignupForm):
      """ django-allauth usage defined in settings in ACCOUNT_FORMS"""
      title = forms.CharField(label=_('Title'), widget=forms.Select(choices=choices.USER_TITLE))
      first_name = forms.CharField(label=_('First Name'))
      last_name = forms.CharField(label=_('Last Name'))
      email = forms.EmailField(widget=forms.TextInput(attrs={'type': 'email',}))
      password1 = SetPasswordField(label=_("Password"))
      password2 = CustomPasswordField(label=_("Password (again)"))
  
      def __init__(self, *args, **kwargs):
  
          super(SignupForm, self).__init__(*args, **kwargs)
          set_form_field_order(self, ["title", "first_name", "last_name", "email", "password1", "password2"])
          for field in self.fields:
              self.fields[field].widget.attrs['class'] = 'mdl-textfield__input'
  
      class Meta:
          fields = ('title', 'first_name', 'last_name', 'email', 'password1', 'password2')
  </code></pre>
  
  <p>We use default allauth LoginForm and LoginView.</p>
  
  <p>It's Django 1.8.7, nginx (1 process), gunicorn (4 workers) running through supervisor (as 1 process).</p>