Replace Entropy with RAND_bytes

/dev/urandom is not an approved random number generator
for NIAP certification. Changing to use BoringSSL's
RAND_bytes(), which is approved.

Bug: 121272336
Test: Ran Keystore CTS tests against Walleye
Change-Id: I579d140ef56c90b477b0d8989e3b02375681aee8
diff --git a/keystore/KeyStore.h b/keystore/KeyStore.h
index d2049a4..25ff3a5 100644
--- a/keystore/KeyStore.h
+++ b/keystore/KeyStore.h
@@ -75,7 +75,7 @@
 
 class KeyStore : public ::android::IBinder::DeathRecipient {
   public:
-    KeyStore(Entropy* entropy, const KeymasterDevices& kmDevices,
+    KeyStore(const KeymasterDevices& kmDevices,
              SecurityLevel minimalAllowedSecurityLevelForNewKeys);
     ~KeyStore();
 
@@ -148,7 +148,6 @@
     static const char* kMetaDataFile;
     static const android::String16 kRsaKeyType;
     static const android::String16 kEcKeyType;
-    Entropy* mEntropy;
 
     KeymasterWorkers mKmDevices;