Fix loading AWS libraries to improve performance

[jakubboucek]

Change initiate AWS SDK from handler to parser time. That can use native Node code-cache and this is not included to billed duration.

Practical result:

Before
Duration: 4931.01 ms Billed Duration: 5000 ms Memory Size: 128 MB Max Memory Used: 56 MB
After
Duration: 2601.95 ms Billed Duration: 2700 ms Memory Size: 128 MB Max Memory Used: 32 MB

[arithmetric]

Thanks!