Use the given timeout value for proxy calls

[kushaldas]

Right now we don't pass the given timeout value to the proxy object calls. We should pass the value to the proxy object.

Related PR in the securedrop-proxy freedomofpress/securedrop-proxy#69

[kushaldas]

While working on this I figured somehow in the past we missed to update the test cases for sdk in many places, causing many different new errors. Trying to debug those one by one.

[kushaldas]

https://github.com/freedomofpress/securedrop-proxy/blob/master/securedrop_proxy/proxy.py#L272-L278

When we send in an unencrypted error to the securedrop server, it replies with a "BAD REQUEST 400" and a JSON message. We were dependent on that error message before to provide the information that it missing encryption, but, that is now not happing due to the code mentioned above in the proxy. In particular this line, https://github.com/freedomofpress/securedrop-proxy/blob/3a79ea4cdc7bddd13c8536184defb7a3f5c2f2d2/securedrop_proxy/proxy.py#L277

For now I will just modify the test for error in uncrypted reply for the same in APIProxy.