added checks for the presence of the security agent before calling se…

[nr-swilloughby]

Since the fix to the race condition mentioned in PR 754 needs to lock and unlock a Transaction mutex each time a segment is created, this PR adds a check first so that if there is no security agent installed at all, we don't attempt the security call at all, removing the race condition and mutex overhead in that case. If a security agent is installed, then the mutex-protected code will be used to prevent the race condition.

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (develop@99f46e0). Click here to learn what that means.
The diff coverage is n/a.

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