Missing checks exporting

[thiagoftsm]

Summary

This PR brings the missing tests to returns for uv_ functions as specified at #8461.

Component Name

Exporting

Test Plan

1 - Start hbase
2 - Start zookeper
3 - Start opentsdb running: ./tsdb tsd --port=4242 --staticroot=staticroot/ --cachedir=/tmp/tsd --zkquorum=localhost:2181 --auto-metric
4 - Start JSON backend running: nc -lntp 5448
5 - Start MongoDB: The command here depends of the distribution.
6 - Configure exporting.conf:

[exporting:global]
    enabled = yes
    send configured labels = yes
    send automatic labels = no

[json:my_instance]
    enabled = yes
    destination = localhost:5448

[opentsdb:http:my_instance2]
    enabled = yes
    destination = localhost:4242

[mongodb:instanceA]
    enabled = yes
    destination = mongodb://localhost
    database = netdata
    collection = instanceA

@vlvkobal , please, update the example bringing the options for AWS.

7 - Start Netdata
8 - Verify all the exporters received the data.

Additional Information

This PR does not brings everything listed on #8461 and it is not a blocker for any other action there.

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Test this branch here: https://thiagoftsmmissing-checks-expor-r48jc.squash.io