Add namespace to GetDefaultDomain

Test: Local build and boot
Change-Id: Ib6acb27dd2e2a29664a3be8151e2b223dd728a11
diff --git a/host/commands/launch/main.cc b/host/commands/launch/main.cc
index 1a2cffe..5177238 100644
--- a/host/commands/launch/main.cc
+++ b/host/commands/launch/main.cc
@@ -443,9 +443,9 @@
   }
   if (FLAGS_dtb.empty()) {
     if (FLAGS_initrd.empty()) {
-      FLAGS_dtb = DefaultHostArtifactsPath("config/system-root.dtb");
+      FLAGS_dtb = vsoc::DefaultHostArtifactsPath("config/system-root.dtb");
     } else {
-      FLAGS_dtb = DefaultHostArtifactsPath("config/initrd-root.dtb");
+      FLAGS_dtb = vsoc::DefaultHostArtifactsPath("config/initrd-root.dtb");
     }
   }
   if (FLAGS_cache_image.empty()) {