Shenandoah fails some vmTestbase_nsk_jvmti tests with "assert(!ShenandoahThreadLocalData::is_evac_allowed(Thread::current())) failed: sanity"

SYNOPSIS IS PROVISIONAL, CHANGE ONCE YOU IDENTIFY THE ISSUE

$ make images run-test TEST=vmTestbase_nsk_jvmti TEST_VM_OPTS="-XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC"

# Internal Error (/home/shade/trunks/jdk-jdk/src/hotspot/share/gc/shenandoah/shenandoahEvacOOMHandler.cpp:54), pid=32402, tid=32425
# assert(!ShenandoahThreadLocalData::is_evac_allowed(Thread::current())) failed: sanity
#
# JRE version: OpenJDK Runtime Environment (15.0) (fastdebug build 15-internal+0-adhoc.shade.jdk-jdk)
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 15-internal+0-adhoc.shade.jdk-jdk, mixed mode, sharing, tiered, compressed oops, shenandoah gc, linux-amd64)
# Problematic frame:
# V [libjvm.so+0x1491fa4] ShenandoahEvacOOMHandler::enter_evacuation()+0x1d4

urrent thread (0x00007ff4d4002800): GCTaskThread "Shenandoah GC Threads#2" [stack: 0x00007ff4d1eb4000,0x00007ff4d1fb4000] [id=32425]

Stack: [0x00007ff4d1eb4000,0x00007ff4d1fb4000], sp=0x00007ff4d1fb28a0, free space=1018k
Native frames: (J=compiled Java code, A=aot compiled Java code, j=interpreted, Vv=VM code, C=native code)
V [libjvm.so+0x1491fa4] ShenandoahEvacOOMHandler::enter_evacuation()+0x1d4
V [libjvm.so+0x1429875] ShenandoahBarrierSet::load_reference_barrier_impl(oop)+0x155
V [libjvm.so+0x1429b7b] ShenandoahBarrierSet::load_reference_barrier_not_null(oop)+0x7b
V [libjvm.so+0x142d619] oop ShenandoahBarrierSet::load_reference_barrier_native_impl<oop>(oop, oop*)+0x89
V [libjvm.so+0x1429e24] ShenandoahBarrierSet::load_reference_barrier_native(oop, oop*)+0x34
V [libjvm.so+0x80adc7] AccessInternal::PostRuntimeDispatch<ShenandoahBarrierSet::AccessBarrier<1187956ul, ShenandoahBarrierSet>, (AccessInternal::BarrierType)2, 1187956ul>::oop_access_barrier(void*)+0x67
V [libjvm.so+0xfa063f] JvmtiTagMap::do_weak_oops(BoolObjectClosure*, OopClosure*)+0x24f
V [libjvm.so+0xfa09ee] JvmtiTagMap::weak_oops_do(BoolObjectClosure*, OopClosure*)+0xae
V [libjvm.so+0x14e8086] ShenandoahRootEvacuator::roots_do(unsigned int, OopClosure*)+0x6c6
V [libjvm.so+0x14a86ff] ShenandoahEvacuateUpdateRootsTask::work(unsigned int)+0xcf
V [libjvm.so+0x17c7430] GangWorker::loop()+0xe0
V [libjvm.so+0x1693b76] Thread::call_run()+0xf6
V [libjvm.so+0x1296896] thread_native_entry(Thread*)+0x116


Failing tests:
 vmTestbase/nsk/jvmti/unit/heap/BasicTagTests.java
 vmTestbase/nsk/jvmti/scenarios/allocation/AP10/ap10t001.java
 vmTestbase/nsk/jvmti/scenarios/allocation/AP12/ap12t001.java