Remove <Unknown> entry from Authentication Status box.

Remove <Unknown> entry from Authentication Status box, these entries were for keypairs(AuthKeyPairAmazon), and had null in authtype field in the table.

https://bugzilla.redhat.com/show_bug.cgi?id=1158180
https://bugzilla.redhat.com/show_bug.cgi?id=1158179
Merge pull request #1218 from h-kataria/remove_unknown_credentials_from_cloud_summary

Remove <Unknown> entry from Authentication Status box.