OCPBUGS-1482: Don't override schedulableMasters unnecessarily (#4414)

When generating the Ignition files, the installer already sets
schdulableMasters to true when there are no worker nodes (i.e. in the
SNO and compact cluster topologies. (See
openshift/installer#2004) Therefore it is
unnecessary to override it here (though it may be preferred to avoid a
warning log from the installer).

Since openshift/installer#6247, attempting to
override the schedulableMasters setting causes installation to fail,
because there are two manifests of the same type and name that conflict.

Since we don't need to set this override when the installer would
already do it, avoid doing so and triggering the error when the value is
determined by the number of hosts rather than explicitly set by the
user.

The conflict still needs to be resolved so that the user can enable
schedulableMasters, but this at least allows the SNO and compact
topologies to install OpenShift 4.12 again.

This partially reverts commit c45f369.

Author: zaneb

internal/common/common.go

@@ -120,7 +120,14 @@ func IsImportedCluster(cluster *Cluster) bool {
 }
 
 func AreMastersSchedulable(cluster *Cluster) bool {
-	return swag.BoolValue(cluster.SchedulableMastersForcedTrue) || swag.BoolValue(cluster.SchedulableMasters)
+	// If the topology forces schedulable masters (i.e. there are no workers),
+	// SchedulableMastersForcedTrue will be true, but also it will be enabled
+	// by default in the installer. Since overriding it currently causes a
+	// failure due to a conflict starting with 4.12, we prefer to avoid it. We
+	// only need to override the installer when the user has set
+	// SchedulableMasters explicitly and that is not already the default in the
+	// installer.
+	return !swag.BoolValue(cluster.SchedulableMastersForcedTrue) && swag.BoolValue(cluster.SchedulableMasters)
 }
 
 func GetEffectiveRole(host *models.Host) models.HostRole {

internal/common/common_test.go

@@ -253,8 +253,8 @@ var _ = Describe("Test AreMastersSchedulable", func() {
 		}{
 			{schedulableMastersForcedTrue: false, schedulableMasters: false, expectedSchedulableMasters: false},
 			{schedulableMastersForcedTrue: false, schedulableMasters: true, expectedSchedulableMasters: true},
-			{schedulableMastersForcedTrue: true, schedulableMasters: false, expectedSchedulableMasters: true},
-			{schedulableMastersForcedTrue: true, schedulableMasters: true, expectedSchedulableMasters: true},
+			{schedulableMastersForcedTrue: true, schedulableMasters: false, expectedSchedulableMasters: false}, // Handled by installer
+			{schedulableMastersForcedTrue: true, schedulableMasters: true, expectedSchedulableMasters: false},  // Handled by installer
 		} {
 			test := test
 			It(fmt.Sprintf("schedulableMastersForcedTrue=%v schedulableMasters=%v AreMastersSchedulable? %v", test.schedulableMastersForcedTrue, test.schedulableMasters, test.expectedSchedulableMasters), func() {