Fix isCryptoSchemeSupported's return value.

If mimeType is not defined, isCryptoSchemeSupported will always
return false.

Test: Netflix on Fugu

Test:
ANDROID_BUILD_Troid-gts/tools/gts-tradefed run gts -m GtsMediaTestCases
--test com.google.android.media.gts.MediaDrmTest#testWidevineSanity

bug: 35363342
Change-Id: I579dd6d41d17c1520404a5b45baae3f730f8245a
diff --git a/drm/libmediadrm/DrmHal.cpp b/drm/libmediadrm/DrmHal.cpp
index 73dc93b..8200d55 100644
--- a/drm/libmediadrm/DrmHal.cpp
+++ b/drm/libmediadrm/DrmHal.cpp
@@ -349,6 +349,7 @@
     bool result = false;
 
     if (mFactory != NULL && mFactory->isCryptoSchemeSupported(uuid)) {
+        result = true;
         if (mimeType != "") {
             result = mFactory->isContentTypeSupported(mimeType.string());
         }