Use continuous clock for memory persist driver (#497)

* Use continuous clock for memory persist driver

* Change default clock to continuous

Sources/Hummingbird/Storage/MemoryPersistDriver.swift

@@ -18,7 +18,7 @@ import NIOCore
 
 /// In memory driver for persist system for storing persistent cross request key/value pairs
 public actor MemoryPersistDriver<C: Clock>: PersistDriver where C.Duration == Duration {
-    public init(_ clock: C = .suspending) {
+    public init(_ clock: C = .continuous) {
         self.values = [:]
         self.clock = clock
     }