Truncate files when restarting a HTTP transfer

Dependencies

• [2] TPEH2XNB 1.0.0-alpha.28, with Tokio 1.0
• [3] IQ4FCHPZ HTTP connections: pooling + retry on error
• [4] VBMXB443 Retrying if the HTTP connection drops while reading the body
• [*] FBXYP7QM Forgot to add remote::http

Change contents

• replacement in pijul/src/remote/http.rs at line 36
  [3.730]→[3.730:803](∅→∅)
  − error!("HTTP error, retrying in {} seconds", delay.round());
  [3.730]

  [2.1132]
  + debug!("HTTP error, retrying in {} seconds", delay.round());
• edit in pijul/src/remote/http.rs at line 38
  [2.1213]

  [3.888]
  + f.set_len(0)?;