metadatasvc: wrapped initCrypto with log.Fatal

In case the HMAC key generation fails then do not allow the metadatasvc process execution to continue and print the error.
This avoids any potential security issues if there is not enough entropy in the system.
metadatasvc: checking the initCrypto error

Missed the real checking for the initCrypto error.
I have also taken the liberty to slightly change the printing of the error of the setupIPTables call to keep it consistant and use log.Fatal
metadatasvc: changed from fmt to log the setupIPTables

To keep the error handling consistant on the main function I changed the printing of the error from fmt + return to log.Fatal in the setupIPTables
Merge pull request #138 from silenteh/metadatasvc-initcrypto

metadatasvc: wrapped initCrypto with log.Fatal