distro: add rhel-8.1 support

Images can be built for rhel 8.1. The pipeline generation and distro
tests are based off of the rhel 8.2 ones. Repository information as been
added for rhel 8.1. The repo urls are internal ones and will only work
if the user is on the Red Hat vpn.

internal/common/types.go

@@ -247,6 +247,7 @@ const (
 	Fedora30 Distribution = iota
 	Fedora31
 	Fedora32
+	RHEL81
 	RHEL82
 )
 
@@ -258,6 +259,7 @@ func getDistributionMapping() map[string]int {
 		"fedora-30": int(Fedora30),
 		"fedora-31": int(Fedora31),
 		"fedora-32": int(Fedora32),
+		"rhel-8.1":  int(RHEL81),
 		"rhel-8.2":  int(RHEL82),
 	}
 	return mapping
@@ -269,6 +271,7 @@ func (dist *Distribution) ModulePlatformID() (string, error) {
 		Fedora30: "platform:f30",
 		Fedora31: "platform:f31",
 		Fedora32: "platform:f32",
+		RHEL81:   "platform:el8",
 		RHEL82:   "platform:el8",
 	}
 	id, exists := mapping[*dist]