The heap owned by CmpStatement may be deleted twice

[QF Chen]

This is found during the investigation of a core file found during seabase/TEST015.

#40 <signal handler called>
#41 0x0000000000000571 in ?? ()
#42 0x00007ffff4cfd91b in NATableDB::resetAfterStatement (this=0x7fffe8800678)
    at ../optimizer/NATable.cpp:7529
#43 0x00007ffff4f4cbe4 in SchemaDB::cleanupPerStatement (this=0x7fffe8800668)
    at ../optimizer/SchemaDB.cpp:186
#44 0x00007ffff3e02cc7 in CmpContext::cleanup (this=0x7fffe87fb090, exception=0)
    at ../arkcmp/CmpContext.cpp:488
#45 0x00007ffff3e02bbe in CmpContext::unsetStatement (this=0x7fffe87fb090, s=
    0x7fffded33f48, exceptionRaised=0) at ../arkcmp/CmpContext.cpp:452
#46 0x00007ffff3e0de4b in CmpStatement::~CmpStatement (this=0x7fffded33f48,
    __in_chrg=<value optimized out>) at ../arkcmp/CmpStatement.cpp:224
#47 0x00007ffff3e0dee2 in CmpStatement::~CmpStatement (this=0x7fffded33f48,
    __in_chrg=<value optimized out>) at ../arkcmp/CmpStatement.cpp:227
#48 0x00007ffff3dfd7a0 in ExCmpMessage::actOnReceive (this=0x7fffffffbb70)
    at ../arkcmp/CmpConnection.cpp:588
#49 0x00007ffff723e191 in IpcMessageStream::internalActOnReceive (
    this=0x7fffffffbb70, buffer=0xba8bd0, connection=0xbb0920)
    at ../common/Ipc.cpp:3553
#50 0x00007ffff723c0b7 in IpcMessageBuffer::callReceiveCallback (this=0xba8bd0,
    conn=0xbb0920) at ../common/Ipc.cpp:2427
#51 0x00007ffff72501a0 in GuaConnectionToClient::acceptBuffer (this=0xbb0920,
    buffer=0xba8bd0, receivedDataLength=504) at ../common/IpcGuardian.cpp:2467
#52 0x00007ffff7251bb7 in GuaReceiveControlConnection::wait (this=0xba0150,
    timeout=-1, eventConsumed=0x0, ipcAwaitiox=0x0)
    at ../common/IpcGuardian.cpp:3164
#53 0x00007ffff724f5be in GuaConnectionToClient::wait (this=0xbb0920,

Root cause analysis.

CmpStatement::~CmpStatement() deletes the heap (statement heap) before makes a call to
context_->unsetStatement(this,exceptionRaised_), which indirectly call NATableDB::resetAfterStatement(),
which deletes the contained heap_ object for each NATable on cached statement list and tabeToDeleteList.
When the contained heap is the statement heap, the compiler cores.