Add basic integration tests for all endpoints

[rzats]

This PR #1062 had some endpoints with missing imports, but passed integration testing. We should make sure all endpoints are covered by basic integration tests ("doesn't throw an error") to prevent this from happening.

Missing imports were fixed in #1067.

Starter list of endpoints:

• afhsb (table doesn't exist; Disable/remove afhsb endpoint #1141 to remove)
• cdc
• covid_hosp_facility
• covid_hosp_facility_lookup
• covid_hosp_state_timeseries
• covidcast
• covidcast/meta
• TODO: list additional covidcast/ endpoints from covidcast.py
• covidcast_meta (different from covidcast/meta)
• covidcast_nowcast
• delphi
• dengue_nowcast
• dengue_sensors
• ecdc_ili
• flusurv
• fluview
• fluview_clinical
• fluview_meta
• gft
• ght
• ilinet (replaced with fluview)
• kcdc_ili
• meta
• meta_afhsb (table doesn't exist; Disable/remove afhsb endpoint #1141 to remove)
• meta_norostat
• nidss_dengue
• nidss_flu
• norostat
• nowcast
• paho_dengue
• quidel
• sensors
• signal_dashboard_coverage
• signal_dashboard_status
• twitter
• wiki

For each we need to:

1. see if it has coverage in integration tests
2. if so, check it off
3. if not, add a test, then check it off

[melange396]

possibly helpful: Dmitry "dug through the old endpoints and got one non-trivial response query for almost all of them" (slack message)

[melange396]

done in #1241