Simplify test http_server_properties member access.

Append underscore to the name of
QuicNetworkTransactionTest::http_server_properties member to match other
members.  Use it directly instead of *(session_->http_server_properties)
throughout tests.

BUG=

Review URL: https://codereview.chromium.org/1130783008

Cr-Commit-Position: refs/heads/master@{#330078}
1 file changed