Do not generate import base interface to vts file.

Bug:33752734
Test: make hidl-gen, manually check the generated vts file.
Change-Id: I91ba609aeb46db34b22b702588fc7e009c3f29d9
diff --git a/generateVts.cpp b/generateVts.cpp
index d2e943f..5224d17 100644
--- a/generateVts.cpp
+++ b/generateVts.cpp
@@ -111,7 +111,10 @@
     out << "package: \"" << mPackage.package() << "\"\n\n";
 
     for (const auto &item : mImportedNames) {
-        out << "import: \"" << item.string() << "\"\n";
+        // ignore IBase.
+        if (item != gIBaseFqName) {
+            out << "import: \"" << item.string() << "\"\n";
+        }
     }
 
     out << "\n";