mzcompose: Reduce overheads for small runs (33.9s -> 10.2s)

[def-]

Targetting downing and upping services

With nothing running: bin/mzcompose --find testdrive down: 1.9s -> 0.5s
With an empty file: bin/mzcompose --find testdrive run default empty.td: 20.0s -> 8.1s
After a run: bin/mzcompose --find testdrive down: 12.0s -> 1.6s

[github-actions]

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