Fix json merge warnings

[jswoods]

We get these warnings in the fluentbit logs:

[debug] [filter_kube] could not merge JSON log as requested

Looks like this may be solved by fluent/fluent-bit#692, which was originally reported here: fluent/fluent-bit#691.

[jstroem]

This is still a problem with the latest fluentbit version (1.13.6) we ended up disabling the merge and handling the parsing in humio