The deadlock happens from time to time, when converting documents
containing OLE objects via remote UNO (from Java) -- after the
conversion, when closing the document.

The relevant stacktraces are:

>Debug.ListCallStack /ShowLineOffset /AllThreads
Callstack for Thread 8 (Thread Id: 32912 (0x8090)):
...
 6      sal3.dll!osl_acquireMutex(_oslMutexImpl * Mutex) Line 75
 7      [Inline Frame] emboleobj.dll!osl::Mutex::acquire() Line 56
 8      [Inline Frame] emboleobj.dll!osl::Guard<osl::Mutex>::{ctor}(osl::Mutex &) Line 129
 9      emboleobj.dll!OleComponent::OnClose_Impl() Line 1399
 10     emboleobj.dll!OleWrapperAdviseSink::OnClose() Line 119

Callstack for Thread 11 (Thread Id: 21088 (0x5260)):
...
 11     ole32.dll!00007fffc5e44e83()
 12     [Inline Frame] emboleobj.dll!OleComponent::CloseObject() Line 1012
 13     emboleobj.dll!OleComponent::Dispose() Line 484
 14     emboleobj.dll!OleComponent::close(unsigned char bDeliverOwnership) Line 1463
 15     emboleobj.dll!OleEmbeddedObject::GetRidOfComponent() Line 239
 16     emboleobj.dll!OleEmbeddedObject::Dispose() Line 275
 17     emboleobj.dll!OleEmbeddedObject::close(unsigned char bDeliverOwnership) Line 497
...
 26     swlo.dll!SwXTextDocument::close(unsigned char bDeliverOwnership) Line 617

OleComponent::OnClose_Impl() taking a lock is fine, but
OleComponent::close() takes a lock and then later it still calls out
(via OleComponent::CloseObject()), which is a no-go.

Fix the problem by making sure that callers of Dispose() own no lock at
the time of the function call, and taking the lock in Dispose() only
after the CloseObject() call (which invokes event listeners).

Change-Id: I53befee21478188c7f79723b7d7596e66077d1c2
Reviewed-on: https://gerrit.libreoffice.org/63014
Tested-by: Jenkins
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>