MDB hangs asking data from I_S.columnstore_extents or I_S.columnstore_files

The problem happens when MCS is restarted but MDB isn't. This causes MDB to point to the deleted BRM segments in shmem b/c MCS recreates them.
4QA To reproduce run MDB+MCS, restart MCS but not MDB and then run this bash snippet to fill ExtentMap

for e in $(seq 0 50); do mysql -e 'create table cs1(i bigint, i2 bigint, i3 bigint, i4 bigint)engine=columnstore' test; mysql -e 'drop table cs1' test; done

Then try to query from information_schema.columnstore_extents. MDB must hang after this.