fix(test_ami): Bump socket startup timeout to 90 seconds.

I've observed networking between ec2 instances not start working for
somewhere between 40-50 seconds earlier today which caused the test to
fail despite the fact that everything came up properly eventually.
Upping to 90 seconds should better cope with the surprises Amazon has to
offer.
Merge pull request #93 from marineam/timeout

fix(test_ami): Bump socket startup timeout to 90 seconds.