Rework session keep-alive logic (#1359)

we don't really know what the server expects and how quickly it usually reacts, so add some safety margin to avoid timing out too early

Author: wisp3rwind

Cargo.lock

@@ -44,6 +44,7 @@ num-traits = "0.2"
 once_cell = "1"
 parking_lot = { version = "0.12", features = ["deadlock_detection"] }
 pbkdf2 = { version = "0.12", default-features = false, features = ["hmac"] }
+pin-project-lite = "0.2"
 priority-queue = "2.0"
 protobuf = "3.5"
 quick-xml = { version = "0.36.1", features = ["serialize"] }