matrix: audit timeouts

[jahschwa]

Specifically encountered during a room join:

2019-05-12 15:46:56 | sibylbot | DEB | Running rooms hook: sibylbot._SibylBot__tell_errors
2019-05-12 15:49:06 | sibylbot | ERR | Error joining room "matrix:!room1:domain.net" (
    Something went wrong in POST requesting https://domain.net/_matrix/client/r0/join/%21room1%3Adomain.net:
    HTTPSConnectionPool(host='domain.net', port=443):
    Max retries exceeded with url: /_matrix/client/r0/join/%21room1%3Adomain.net?access_token=REDACTED (
        Caused by NewConnectionError(
            '<urllib3.connection.VerifiedHTTPSConnection object at 0x7f1390a60c90>:
            Failed to establish a new connection: [Errno 110] Connection timed out',
        )
    )
)

Because sibyl is single threaded, that tied up the bot for a full 2 minutes during startup, which is less than ideal. However, this might not be easily fixable, given this is still open: https://github.com/matrix-org/matrix-python-sdk/pull/157