dashboard: mark netbsd-arm-bsiegert and netbsd-arm64-bsiegert with FlakyNet

These builders have both exhibited multiple 'i/o timeout' errors
contacting www.google.com in net.TestLookupHostCancel.

Updates golang/go#50191.

Change-Id: I3d5ef2940f8c6df3487743a26f64d1e38fdcb231
Reviewed-on: https://go-review.googlesource.com/c/build/+/409474
TryBot-Result: Gopher Robot <[email protected]>
Auto-Submit: Bryan Mills <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Run-TryBot: Bryan Mills <[email protected]>

Author: Bryan C. Mills

dashboard/builders.go

@@ -2182,6 +2182,7 @@ func init() {
 			// The machine is slow.
 			"GO_TEST_TIMEOUT_SCALE=10",
 		},
+		FlakyNet: true,
 	})
 	addBuilder(BuildConfig{
 		Name:           "netbsd-arm64-bsiegert",
@@ -2192,6 +2193,7 @@ func init() {
 			// The machine is slow.
 			"GO_TEST_TIMEOUT_SCALE=10",
 		},
+		FlakyNet: true,
 	})
 	addBuilder(BuildConfig{
 		Name:           "plan9-386",