Replace logsrvd_is_early() with logsrvd_warn_stderr().

This is now defined in logsrvd_conf.c which removes a dependency
on another compilation unit for the fuzzer.

logsrvd/regress/fuzz/fuzz_logsrvd_conf.c

@@ -41,12 +41,6 @@
 #include "log_server.pb-c.h"
 #include "logsrvd.h"
 
-bool
-logsrvd_is_early(void)
-{
-    return true;
-}
-
 int
 LLVMFuzzerTestOneInput(const uint8_t *data, size_t size)
 {