The `spel_amigenfstype` user-variable is not fully implemented

[ferricoxide]

Expected behavior

Setting a value for spel_amigenfstype results in the produced-AMI's root-filesystems all be formatted with the selected fstype

Actual behavior

While the spel_amigenfstype user-variable is referenced in the AMI-builders for EL8 (minimal-centos-8-hvm and minimal-rhel-8-hvm), they are:

• Not actually defined in the user-variable definition-section
• Not referenced in any of the other builders.

Suggestions for fix

1. Add the spel_amigenfstype variable-declare (likely with default value of ext4) to the user-variables section
2. Ensure:

   "SPEL_AMIGENFSTYPE={{ user `spel_amigenfstype` }}"`
   

   is present in all of the builder-definitions

[ferricoxide]

Tagging @nortiz34 for his awareness