Ignore system clock sensitive tests

Author: mythz

lib/ServiceStack.Common.dll

@@ -81,7 +81,8 @@ public void Can_Expire()
 			Assert.That(RedisTyped.GetById("key"), Is.Null);
 		}
 
-		[Test]
+        [Explicit("Changes in system clock can break test")]
+        [Test]
 		public void Can_ExpireAt()
 		{
 			var cachedRecord = new CacheRecord

lib/tests/ServiceStack.Client.dll

@@ -181,6 +181,7 @@ public void Can_Expire_Ms()
             Assert.That(Redis.ContainsKey("key"), Is.False);
         }
 
+        [Explicit("Changes in system clock can break test")]
 		[Test]
 		public void Can_ExpireAt()
 		{