Turn off goaway_sessions_on_ip_change explicitly in iOS migration tests.

http://crbug.com/c/1769725 forces check the caller does not set options
to handle ip address change and connection migration simultaneously. iOS
however enables "goaway_sessions_on_ip_change" be default, which caused
the migration option setting test fails.

Bug: 998156
Change-Id: I8968a257c555b165ecca3aa60138366960c00b0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1773343
Auto-Submit: Zhongyi Shi <zhongyi@chromium.org>
Reviewed-by: Lily Chen <chlily@chromium.org>
Reviewed-by: Ryan Hamilton <rch@chromium.org>
Commit-Queue: Ryan Hamilton <rch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690878}

components/cronet/url_request_context_config_unittest.cc

@@ -659,7 +659,10 @@ TEST(URLRequestContextConfigTest, SetQuicConnectionMigrationV2Options) {
       // User-Agent request header field.
       "fake agent",
       // JSON encoded experimental options.
+      // Explicitly turn off "goaway_sessions_on_ip_change" which is default
+      // enabled on iOS but cannot be simultaneously set with migration option.
       "{\"QUIC\":{\"migrate_sessions_on_network_change_v2\":true,"
+      "\"goaway_sessions_on_ip_change\":false,"
       "\"migrate_sessions_early_v2\":true,"
       "\"retry_on_alternate_network_before_handshake\":true,"
       "\"migrate_idle_sessions\":true,"