MINOR: deinit: add a "quick-exit" option to bypass the deinit step

MINOR: deinit: add a "quick-exit" option to bypass the deinit step

Once in a while we spot a bug in the deinit code that is complex,
especially when it has to deal with incomplete initializations, and the
ability to bypass this step has regularly been raised. In addition for
fast-reloading setups it could theoretically save some time. Tests have
shown that very large configs can barely save ~100-150ms by skipping the
deinit step. However the ability not to crash if a bug is encountered can
occasionally help.

This patch adds an option to do exactly this. It's obviously not enabled
by default and the documentation discourages from using it, but this might
be useful in the future.