add GetRandBytes() as wrapper for RAND_bytes()

- add a small wrapper in util around RAND_bytes() and replace with
  GetRandBytes() in the code to log errors from calling RAND_bytes()
- remove OpenSSL header rand.h where no longer needed

src/addrman.h

@@ -16,8 +16,6 @@
 #include <stdint.h>
 #include <vector>
 
-#include <openssl/rand.h>
-
 /** Extended statistics about a CAddress */
 class CAddrInfo : public CAddress
 {
@@ -384,7 +382,7 @@ public:
     CAddrMan() : vRandom(0), vvTried(ADDRMAN_TRIED_BUCKET_COUNT, std::vector<int>(0)), vvNew(ADDRMAN_NEW_BUCKET_COUNT, std::set<int>())
     {
          nKey.resize(32);
-         RAND_bytes(&nKey[0], 32);
+         GetRandBytes(&nKey[0], 32);
 
          nIdCount = 0;
          nTried = 0;