Modify test.mk

1. The ethread test can only be ran when both the encoder and decoder are
available. This is also true for ext_tile test.
2. Modify the ethread speed test range to speed 0 to 3 for AV1.

BUG=aomedia:117

Change-Id: I3c3e96fb33a7b825503b228fe43e8089e1265dd2

test/ethread_test.cc

diff --git a/test/ethread_test.cc b/test/ethread_test.cc
index 9b58052..68ae42e 100644
--- a/test/ethread_test.cc
+++ b/test/ethread_test.cc
@@ -176,14 +176,15 @@
 // TODO(thdavies): EC_ADAPT does not support tiles
 
 #else
+// For AV1, only test speed 0 to 3.
 AV1_INSTANTIATE_TEST_CASE(AVxEncoderThreadTest,
                           ::testing::Values(::libaom_test::kTwoPassGood,
                                             ::libaom_test::kOnePassGood),
-                          ::testing::Range(3, 9));
+                          ::testing::Range(2, 4));
 
 AV1_INSTANTIATE_TEST_CASE(AVxEncoderThreadTestLarge,
                           ::testing::Values(::libaom_test::kTwoPassGood,
                                             ::libaom_test::kOnePassGood),
-                          ::testing::Range(0, 3));
+                          ::testing::Range(0, 2));
 #endif
 }  // namespace