Commit 8aad8c claimed to do this, but it checks for the 304 status too early, before handle_conditional_get! has overridden it.

[#958 state:resolved]
Signed-off-by: NJonathan del Strother <jon.delStrother@bestbefore.tv>
Signed-off-by: NJeremy Kemper <jeremy@bitsweat.net>