Fix: unable to restart container after it was killed

When the process name found by the PID file and the PID in the PID file
are the same it should be treated as it is from another process so that
ospd-openvas can be started even after a sudden kill of a container.

To verify this change you can start ospd-openvasby executing:
```
docker run -v /run/redis/redis.sock:/run/redis/redis.sock \
  --name "narf" \
  --privileged greenbone/ospd-openvas:unstable ospd-openvas -f
```

Then kill it via:

```
docker kill narf
```

and restart it with

```
docker start -a narf
```

Fixes: #725

Author: nichtsfrei

ospd/misc.py

@@ -103,22 +103,23 @@ def create_pid(pidfile: str) -> bool:
     Otherwise gives an error."""
 
     pid = str(os.getpid())
-    new_process = psutil.Process(int(pid))
-    new_process_name = new_process.name()
+    current_process = psutil.Process(int(pid))
+    current_process_name = current_process.name()
 
     pidpath = Path(pidfile)
+    pf_process_name = ""
+    pf_pid = ""
 
     if pidpath.is_file():
-        process_name = None
-        with pidpath.open('r', encoding='utf-8') as pidfile:
-            current_pid = pidfile.read()
+        with pidpath.open('r', encoding='utf-8') as file:
+            pf_pid = file.read()
             try:
-                process = psutil.Process(int(current_pid))
-                process_name = process.name()
+                process = psutil.Process(int(pf_pid))
+                pf_process_name = process.name()
             except psutil.NoSuchProcess:
                 pass
 
-        if process_name == new_process_name:
+        if pf_process_name == current_process_name and pf_pid != pid:
             logger.error(
                 "There is an already running process. See %s.",
                 str(pidpath.absolute()),
@@ -130,9 +131,9 @@ def create_pid(pidfile: str) -> bool:
                 "the process %s. It seems that %s was abruptly stopped. "
                 "Removing the pid file.",
                 str(pidpath.absolute()),
-                current_pid,
-                process_name,
-                new_process_name,
+                pf_pid,
+                pf_process_name,
+                current_process_name,
             )
 
     try: