[tools] Honour default-ttl in pdnsutil load-zone

[miodvallat]

Short description

This trivial mechanical PR lets pdnsutil load-zone default to the default-ttl setting as the TTL value for entries lacking a TTL, if $TTL is not set in the file being loaded.

This addresses #8494.

Checklist

I have:

• read the CONTRIBUTING.md document
• compiled this code
• tested this code
• included documentation (including possible behaviour changes)
• documented the code
• added or modified regression test(s)
• added or modified unit test(s)

[coveralls]

Pull Request Test Coverage Report for Build 14243186746

Details

• 3 of 3 (100.0%) changed or added relevant lines in 1 file are covered.
• 65 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+11.4%) to 63.474%

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Files with Coverage Reduction	New Missed Lines	%
pdns/recursordist/test-syncres_cc1.cc	6	89.64%
pdns/recursordist/taskqueue.cc	9	35.9%
pdns/recursordist/syncres.cc	16	80.11%
pdns/recursordist/rec-taskqueue.cc	34	40.14%

Totals
Change from base Build 14230500445:	11.4%
Covered Lines:	128512
Relevant Lines:	167798

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💛 - Coveralls