Speedup execution of bootsteps

[Ayanda-D]

Proposed Changes

This improves speed of bootstep execution by factor of 2N, where N is
number of attributes per step, matching the passed AttributeName.
Overall time complexity remains O(N), dropping constant from O(2N),
but we don't expect N to be significantly large enough to neglect the
constant for modules with multiple attributes.

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[michaelklishin]

Thank you!

[michaelklishin]

Backported to v3.8.x and v3.7.x.