Fix dlext.ns_smoke test

Check for updated error_message

Bug: http://b/31097098
Test: adb shell bionic-unit-tests32/64 --gtest_filter=dlext.ns*
(cherry picked from commit 3a6c6b3254b2033a9a0246013a2c8b486800624b)

Change-Id: I0f0dd59a6deba016d37d0ccc80113b62db86c1c2
diff --git a/tests/dlext_test.cpp b/tests/dlext_test.cpp
index ee61d5f..5501c8e 100644
--- a/tests/dlext_test.cpp
+++ b/tests/dlext_test.cpp
@@ -628,7 +628,9 @@
 
   ASSERT_FALSE(android_init_namespaces(path.c_str(), nullptr));
   ASSERT_STREQ("android_init_namespaces failed: error initializing public namespace: "
-               "\"libnstest_public.so\" was not found in the default namespace", dlerror());
+               "a library with soname \"libnstest_public.so\" was not found in the "
+               "default namespace",
+               dlerror());
 
   const std::string lib_path = std::string(getenv("ANDROID_DATA")) + NATIVE_TESTS_PATH;