mssqlvdi: Fix IClientVirtualDeviceSet2::CreateEx call.

Seems we need to call IClientVirtualDeviceSet2::CreateEx with as first
argument the instance name when connecting to the an non default
instance.

Fixes #383: mssqldvi problem with connection to mssql not default
            instance

AUTHORS

@@ -75,6 +75,7 @@ Jose Luis Tallon
 Josip Almasi
 Juan Luis Frances
 Juergen Lock
+Jyri Palis
 Karl Cunningham
 Kern Sibbald
 Kjetil Torgrim Homme

src/win32/plugins/filed/mssqlvdi-fd.c

@@ -1429,7 +1429,16 @@ static inline bool setup_vdi_device(bpContext *ctx, struct io_pkt *io)
    /*
     * Create the VDI device set.
     */
-   hr = p_ctx->VDIDeviceSet->CreateEx(NULL, p_ctx->vdsname, &p_ctx->VDIConfig);
+   if (bstrcasecmp(p_ctx->instance, DEFAULT_INSTANCE)) {
+      hr = p_ctx->VDIDeviceSet->CreateEx(NULL, p_ctx->vdsname, &p_ctx->VDIConfig);
+   } else {
+      POOLMEM *instance_name;
+
+      instance_name = get_pool_memory(PM_NAME);
+      UTF8_2_wchar(&instance_name, p_ctx->instance);
+      hr = p_ctx->VDIDeviceSet->CreateEx((LPCWSTR)instance_name, p_ctx->vdsname, &p_ctx->VDIConfig);
+      free_pool_memory(instance_name);
+   }
    if (!SUCCEEDED(hr)) {
       comReportError(ctx, hr);
       return false;