libxl: Fix Xen 4.4 libxlVmStart logic

ifdef LIBXL_HAVE_DOMAIN_CREATE_RESTORE_PARAMS hides a multi-line body
for a brace-less else.  Add braces to ensure proper logic is applied.

Without this fix, new domains cannot be started.  Both
libxl_domain_create_new and libxl_domain_create_restore are called when
starting a new domain leading to this error:
libxl: error: libxl.c:324:libxl__domain_rename: domain with name "guest" already exists.
libxl: error: libxl_create.c:800:initiate_domain_create: cannot make domain: -6

src/libxl/libxl_driver.c

@@ -618,10 +618,10 @@ libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
 
     /* use as synchronous operations => ao_how = NULL and no intermediate reports => ao_progress = NULL */
 
-    if (restore_fd < 0)
+    if (restore_fd < 0) {
         ret = libxl_domain_create_new(priv->ctx, &d_config,
                                       &domid, NULL, NULL);
-    else
+    } else {
 #ifdef LIBXL_HAVE_DOMAIN_CREATE_RESTORE_PARAMS
         params.checkpointed_stream = 0;
         ret = libxl_domain_create_restore(priv->ctx, &d_config, &domid,
@@ -630,6 +630,7 @@ libxlVmStart(libxlDriverPrivatePtr driver, virDomainObjPtr vm,
         ret = libxl_domain_create_restore(priv->ctx, &d_config, &domid,
                                           restore_fd, NULL, NULL);
 #endif
+    }
 
     if (ret) {
         if (restore_fd < 0)