Log: skygw_logmanager_init renamed to mxs_log_init.

skygw_logmanager_init renamed to mxs_log_init and skygw_logmanager_done
renamed to mxs_log_finish. skygw_logmanager_exit removed alltogether as
all it did was to call skygw_logmanager_done. That appears to have been
a source for confusion as in many places a call to skygw_logmanager_done
was followed by a call to skygw_logmanager_exit. In addition, the function
skygw_log_done was removed from the header, since it lacked an
implementation.

server/include/test_utils.h

@@ -12,7 +12,7 @@ void init_test_env(char *path)
 
     const char* logdir = path ? path : TEST_LOG_DIR;
 
-    skygw_logmanager_init(NULL, logdir, LOG_TARGET_DEFAULT);
+    mxs_log_init(NULL, logdir, LOG_TARGET_DEFAULT);
     poll_init();
     hkinit();
 }