Disable man-db updates during package upgrade/installation

[blaedd]

In the worker-startup-script.sh script, on an f1-micro instance, in us-east1, the man-db package postinst and triggers take 7 minutes to run, on first boot. This is a bit of a drag, and an updated mandb doesn't seem essential for these instances.

With the stock startup script.

Dec 16 06:46:08 slow-vm GCEMetadataScripts[378]: 2020/12/16 06:46:08 GCEMetadataScripts: startup-script: Processing triggers for man-db (2.8.5-2) ...
Dec 16 06:52:54 slow-vm GCEMetadataScripts[378]: 2020/12/16 06:52:54 GCEMetadataScripts: startup-script: Processing triggers for dbus (1.12.20-0+deb10u1) ...

With man-db updates triggered by packages disabled.

Dec 16 06:45:37 faster-vm GCEMetadataScripts[374]: 2020/12/16 06:45:37 GCEMetadataScripts: startup-script: Processing triggers 
for man-db (2.8.5-2) ...
Dec 16 06:45:37 faster-vm GCEMetadataScripts[374]: 2020/12/16 06:45:37 GCEMetadataScripts: startup-script: Not building database; man-db/auto-update is not 'true'.
Dec 16 06:45:37 faster-vm GCEMetadataScripts[374]: 2020/12/16 06:45:37 GCEMetadataScripts: startup-script: Processing triggers for dbus (1.12.20-0+deb10u1) ...

[drewhoffer]

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