Reduce usage of TURN_NO_HIREDIS macros (#1022)

`TURN_NO_HIREDIS` is defined when hiredis library is not present and any
redis functionality must be disabled

While all above is correct, it does not require ifdef-ing out all
related code.
For example, redis related fields in `turn_params` do not need to be
compiled out. Same for certain function parameters.

This PR reduces amount of places in code where `TURN_NO_HIREDIS` is used
to make code simpler by moving as much usage of this define into
dbd_redis.h/c files and compiling them unconditionally.

- Always compile/link `dbd_redis.c`
- Move many `TURN_NO_HIREDIS` decisions into `dbd_redis.c`
- Delete empty function redis_async_init

src/apps/common/hiredis_libevent2.c

@@ -167,11 +167,6 @@ static void redisLibeventCleanup(void *privdata)
 
 ///////////////////////// Send-receive ///////////////////////////
 
-void redis_async_init(void)
-{
-	;
-}
-
 int is_redis_asyncconn_good(redis_context_handle rch)
 {
 	if(rch) {

src/apps/common/hiredis_libevent2.h

@@ -48,7 +48,6 @@ typedef void* redis_context_handle;
 
 #if !defined(TURN_NO_HIREDIS)
 
-void redis_async_init(void);
 
 redis_context_handle redisLibeventAttach(struct event_base *base, char *ip, int port, char *pwd, int db);
 

src/apps/relay/CMakeLists.txt

@@ -23,6 +23,7 @@ set(HEADER_FILES
     userdb.h
     dbdrivers/dbdriver.h
     prom_server.h
+    dbdrivers/dbd_redis.h
     )
 
 set(SOURCE_FILES
@@ -39,6 +40,7 @@ set(SOURCE_FILES
     userdb.c
     dbdrivers/dbdriver.c
     prom_server.c
+    dbdrivers/dbd_redis.c
     )
 
 find_package(SQLite)

src/apps/relay/dbdrivers/dbd_redis.c

@@ -1399,4 +1399,7 @@ const turn_dbdriver_t * get_redis_dbdriver(void) {
   return NULL;
 }
 
-#endif
+redis_context_handle get_redis_async_connection(struct event_base *base, redis_stats_db_t* connection_string, int delete_keys) {
+    return NULL;
+}
+#endif /* !defined(TURN_NO_HIREDIS) */

src/apps/relay/dbdrivers/dbd_redis.h

@@ -33,12 +33,14 @@
 #define __DBD_REDIS__
 
 #include "dbdriver.h"
+#include "hiredis_libevent2.h"
 
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 const turn_dbdriver_t * get_redis_dbdriver(void);
+redis_context_handle get_redis_async_connection(struct event_base *base, redis_stats_db_t* connection_string, int delete_keys);
 
 #ifdef __cplusplus
 }

src/apps/relay/dbdrivers/dbdriver.c

@@ -99,11 +99,9 @@ const turn_dbdriver_t * get_dbdriver(void)
 			_driver = get_mongo_dbdriver();
 			break;
 #endif
-#if !defined(TURN_NO_HIREDIS)
 		case TURN_USERDB_TYPE_REDIS:
 			_driver = get_redis_dbdriver();
 			break;
-#endif
 		default:
 			break;
 		}

src/apps/relay/mainrelay.c

@@ -2778,10 +2778,6 @@ int main(int argc, char **argv)
 
 	init_super_memory();
 
-#if !defined(TURN_NO_HIREDIS)
-	redis_async_init();
-#endif
-
 	init_domain();
 	create_default_realm();
 

src/apps/relay/userdb.h

@@ -109,9 +109,7 @@ enum _TURN_USERDB_TYPE {
 #if !defined(TURN_NO_MONGO)
 	,TURN_USERDB_TYPE_MONGO
 #endif
-#if !defined(TURN_NO_HIREDIS)
 	,TURN_USERDB_TYPE_REDIS
-#endif
 };
 
 typedef enum _TURN_USERDB_TYPE TURN_USERDB_TYPE;