Fix zoneinfo parser

[redlicha]

Currently the zoneinfo parser leaves the "zone parsing" state encountering a "pagesets" token. This is however not always present, leading to the parser staying in the "zone parsing" state even when the zone and/or node change.

In addition to that, this MR also adds a number of small fixes spotted by compiling the code with clang, clang analyzer and running it under valgrind.

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[hikerockies]

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