chore(ci): remove flaky tests from failing CI

Cargo.toml

@@ -47,8 +47,10 @@ spmc = "0.2"
 url = "1.0"
 
 [features]
-default = ["runtime"]
-nightly = []
+default = [
+    "__internal_flaky_tests",
+    "runtime",
+]
 runtime = [
     "futures-cpupool",
     "net2",
@@ -58,6 +60,8 @@ runtime = [
     "tokio-tcp",
     "tokio-timer",
 ]
+nightly = []
+__internal_flaky_tests = []
 
 [[example]]
 name = "client"