rpc: do not fail if the pid of the connecting process is not set

getsockopt(sock->fd, SOL_SOCKET, SO_PEERCRED, ...) sets the pid to 0
when the process that opens the connection is in another container.
Signed-off-by: NGiuseppe Scrivano <gscrivan@redhat.com>

src/rpc/virnetsocket.c

@@ -1251,10 +1251,14 @@ int virNetSocketGetUNIXIdentity(virNetSocketPtr sock,
         goto cleanup;
     }
 
-    if (virProcessGetStartTime(cr.pid, timestamp) < 0)
+    *timestamp = -1;
+    if (cr.pid && virProcessGetStartTime(cr.pid, timestamp) < 0)
         goto cleanup;
 
+    if (cr.pid)
         *pid = cr.pid;
+    else
+        *pid = -1;
     *uid = cr.uid;
     *gid = cr.gid;