Fixing the bug with connections on database make restore fail (#473)

* closing the connections that don't need to be open and keeping track of the connections that should stay open

src/Microsoft.SqlTools.ServiceLayer/Connection/FeatureWithFullDbAccess.cs

@@ -0,0 +1,40 @@
+//
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+//
+
+namespace Microsoft.SqlTools.ServiceLayer.Connection
+{
+    /// <summary>
+    /// Any operation that needs full access to databas should implement this interface.
+    /// Make sure to call GainAccessToDatabase before the operation and ReleaseAccessToDatabase after
+    /// </summary>
+    public interface IFeatureWithFullDbAccess
+    {
+        /// <summary>
+        /// Database Lock Manager
+        /// </summary>
+        DatabaseLocksManager LockedDatabaseManager { get; set; }
+
+        /// <summary>
+        /// Makes sure the feature has fill access to the database
+        /// </summary>
+        bool GainAccessToDatabase();
+
+        /// <summary>
+        /// Release the access to db
+        /// </summary>
+        bool ReleaseAccessToDatabase();
+
+        /// <summary>
+        /// Server name
+        /// </summary>
+        string ServerName { get; }
+
+        /// <summary>
+        /// Database name
+        /// </summary>
+        string DatabaseName { get; }
+    }
+
+}