Correct the check for if we still need to set keys

The prior check had an edge case where once keys were pruned, it'd believe the
keys needed to be set ad infinitum.

substrate/client/src/serai/validator_sets.rs

@@ -2,7 +2,7 @@ use sp_core::sr25519::{Public, Signature};
 
 use serai_runtime::{validator_sets, ValidatorSets, Runtime};
 pub use validator_sets::primitives;
-use primitives::{ValidatorSet, KeyPair};
+use primitives::{Session, ValidatorSet, KeyPair};
 
 use subxt::utils::Encoded;
 
@@ -31,6 +31,14 @@ impl Serai {
       .await
   }
 
+  pub async fn get_session(
+    &self,
+    network: NetworkId,
+    at_hash: [u8; 32],
+  ) -> Result<Option<Session>, SeraiError> {
+    self.storage(PALLET, "CurrentSession", Some(vec![scale_value(network)]), at_hash).await
+  }
+
   pub async fn get_validator_set_participants(
     &self,
     network: NetworkId,