sys: process_locker: explicitly don't truncate the lock file

clippy rightfully complains about a create() with an unspecified
truncation behavior. This file has no contents so let's just not
truncate it in case we ever want to also have data in it...

Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>

proxmox-sys/src/process_locker.rs

@@ -112,6 +112,7 @@ impl ProcessLocker {
             .create(true)
             .read(true)
             .write(true)
+            .truncate(false)
             .open(lockfile)?;
 
         Ok(Arc::new(Mutex::new(Self {