Add more information and problem resolution.

The normal behavior of the pidfile is to prevent the daemon to be run twice.
When the ospd-openvas daemon dies unexpectedly or it is killed with SIGKILL (-9) signal,
leaves the pid file, which prevent the daemon to start again.
If this is the case, the pidfile must be removed manually.

ospd/misc.py

@@ -104,7 +104,11 @@ def create_pid(pidfile: str) -> bool:
     pidpath = Path(pidfile)
 
     if pidpath.is_file():
-        LOGGER.error("There is an already running process.")
+        LOGGER.error(
+            "There is an already running process. If no process is running, "
+            "please remove the pid file '%s' manually",
+            str(pidpath.absolute()),
+        )
         return False
 
     try: