restore daemon: use millisecond log resolution

During startup most of the stuff is happening in milliseconds (or
less), so the timestamp granularity of seconds made it hard to tell
if the previous command required 990ms or 1ms, which is quite the
difference in the restore daemon context.

Using micros seems not to bring too much additional information, a
millisecond is already an ok lower time resolution for logging, so
switch only to millis for now.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>
(cherry picked from commit ecd66ecaf6)
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

src/bin/proxmox-restore-daemon.rs

@@ -47,6 +47,7 @@ fn main() -> Result<(), Error> {
     // stdout to a serial terminal attached by QEMU)
     env_logger::from_env(env_logger::Env::default().default_filter_or("info"))
         .write_style(env_logger::WriteStyle::Never)
+        .format_timestamp_millis()
         .init();
 
     // the API may save some stuff there, e.g., the memcon tracking file