Merge pull request #7844 from edx/ahsan/AC-97-aria-describedby-broken-id-ref-sign-in-page

aria-describedby has broken IDref on Sign in email form

lms/templates/student_account/form_field.underscore

@@ -40,7 +40,7 @@
            type="<%= type %>"
            name="<%= name %>"
            class="input-block <% if ( type === 'checkbox' ) { %>checkbox<% } %>"
-           aria-describedby="<%= form %>-<%= name %>-desc"
+            <% if ( type !== 'password' ) { %> aria-describedby="<%= form %>-<%= name %>-desc" <% } %>
             <% if ( restrictions.min_length ) { %> minlength="<%= restrictions.min_length %>"<% } %>
             <% if ( restrictions.max_length ) { %> maxlength="<%= restrictions.max_length %>"<% } %>
             <% if ( required ) { %> aria-required="true" required<% } %>
@@ -52,7 +52,7 @@
             <% if ( placeholder ) { %> placeholder="<%= placeholder %>"<% } %>
             value="<%- defaultValue %>"
         />
-        <% if ( instructions ) { %> <span class="tip tip-input" id="<%= form %>-<%= name %>-instructions"><%= instructions %></span><% } %>
+        <% if ( instructions ) { %> <span class="tip tip-input" id="<%= form %>-<%= name %>-desc"><%= instructions %></span><% } %>
     <% } %>
 
     <% if ( type === 'checkbox' ) { %>