Disable API security by default

[astuyve]

What does this PR do?

This was enabled by default in dd-trace-py, but doesn't apply to lambda and is responsible for about a 128ms cold start increase.
This will disable it unless the user explicitly opts-in.

Motivation

I want this to go fast.

Testing Guidelines

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog
• This PR passes the integration tests (ask a Datadog member to run the tests)

[joeyzhao2018]

LGTM

[joeyzhao2018]

did we compare the resulted cold start time? asking because i wonder if the env is read "early" enough

ignore above. just saw the comparison in slack channel.

[astuyve]

Yeah I had to move it from tracing.py to here