Unclear how useful it is to still be catching BotoServerError exceptions
generally, especially when we are now hopefully handling most instances
of throttling, but kept it as it was already in the code. Moved to main
as catching BotoServerErrors inside individual functions will bypass any
AWSRetry.backoff decorator.
Move additional imports to top.
Use python2.6 formatting
A bit of cleanup on imports
Make one more string interpolation Python 2.6 compatible.
The list_elbs call to boto doesn't use any pagination, so any time there
are more ELBs than the API page size, this module will fail. This change
uses the `next_token` attribute of `ResultSet` to check if there are
still more ELBs to return.
Fixes#21361