MappingIT trips assertion and causes nodes to crash in 7.x bwc tests #60986
Description
While working on a backport, I found that an aspect of the rolling upgrade tests did not work properly so tests that checked the UPGRADE_FROM_VERSION value and executed only when upgrading from 6.x were never being executed. I'm fixing the issue with the rolling upgrade tests in #60927 and will mute MappingIT in the rolling upgrade qa project since it trips an assertion and causes nodes to die.
» fatal error in thread [elasticsearch[v6.8.12-0][clusterApplierService#updateTask][T#1]], exiting
» java.lang.AssertionError: expected current mapping [{"_doc":{"_all":{"enabled":false},"properties":{"field":{"type":"text"}}}}] for type [_doc] to be the same as new mapping [{"_doc":{"properties":{"field":{"type":"text"}}}}]
» at org.elasticsearch.index.mapper.MapperService.assertMappingVersion(MapperService.java:304)
» at org.elasticsearch.index.mapper.MapperService.updateMapping(MapperService.java:215)
» at org.elasticsearch.index.IndexService.updateMapping(IndexService.java:631)
» at org.elasticsearch.indices.cluster.IndicesClusterStateService.updateIndices(IndicesClusterStateService.java:530)
» at org.elasticsearch.indices.cluster.IndicesClusterStateService.applyClusterState(IndicesClusterStateService.java:244)
» at org.elasticsearch.cluster.service.ClusterApplierService.lambda$callClusterStateAppliers$5(ClusterApplierService.java:522)
» at java.base/java.lang.Iterable.forEach(Iterable.java:75)
» at org.elasticsearch.cluster.service.ClusterApplierService.callClusterStateAppliers(ClusterApplierService.java:519)
» at org.elasticsearch.cluster.service.ClusterApplierService.applyChanges(ClusterApplierService.java:490)
» at org.elasticsearch.cluster.service.ClusterApplierService.runTask(ClusterApplierService.java:437)
» at org.elasticsearch.cluster.service.ClusterApplierService.access$100(ClusterApplierService.java:74)
» at org.elasticsearch.cluster.service.ClusterApplierService$UpdateTask.run(ClusterApplierService.java:177)
» at org.elasticsearch.common.util.concurrent.ThreadContext$ContextPreservingRunnable.run(ThreadContext.java:651)
» at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.runAndClean(PrioritizedEsThreadPoolExecutor.java:252)
» at org.elasticsearch.common.util.concurrent.PrioritizedEsThreadPoolExecutor$TieBreakingPrioritizedRunnable.run(PrioritizedEsThreadPoolExecutor.java:215)
» at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
» at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630)
» at java.base/java.lang.Thread.run(Thread.java:832)
The fix to the rolling-upgrade build that provokes this is d05588a.
cc @romseygeek since I see your name in git for this assertion.