Did you manage to solve this? I had to the do the following which forced the connection to be Microsoft.Data.SqlClient by creating it myself. I also pass in true to the base constructor to let the context dispose the connection after.

using System;
using System.Data.Common;
using System.Data.Entity;
using Microsoft.AspNet.Identity.EntityFramework;
using Microsoft.Data.SqlClient;
using Mintsoft.LaunchDarkly;
using Mintsoft.UserManagement.Membership;

namespace Mintsoft.UserManagement
{
    public class UserDbContext : IdentityDbContext<ApplicationUser>
    {
        private static DbConnection GetBaseDbConnection()
        {
            var connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["BaseContext"].ConnectionString;
            return new SqlConnection(connectionString);
        }

        public UserDbContext()
            : base(GetBaseDbConnection(), true)
        {
        }