Fix logic to correctly detect Amazon Linux version
Fix logic to correctly detect Amazon Linux version

Amazon Linux 2 os strings is "amzn_2" and Amazon Linux 1 os string version ID includes the year, for example: "amzn_2016.9".
This was causing all Amazon Linux to detect the binary as if it were Amazon Linux 2 and therefore failing on Amazon Linux 1.
This PR fixes the logic to make the detection work for both versions.
zakird/wkhtmltopdf_binary_gem