Update kafka.yaml: proper spacing & recent changes

With previous spacing check throws exception:
  InvalidJMXConfiguration("Each configuration must have an 'include' section.")

In particular incorporates
DataDog/dd-agent@75863d82ee2f0cdef3f3e75097fe79cb17f6b5c2 - counters-> guages,
DataDog/dd-agent@5382422d3790be2a9c4f6eccb9bca58547ae8c76 - jmxfetch custom tags
and DataDog/dd-agent@8bac88e23f94d615a90e587ed84c55e4adba683f - support for jmxfetch0.4