tdf#116489 - fix ucb TaskManager deadlock.

Change-Id: Ia362db52e7b078203964704569e1d54f053f2b57
Reviewed-on: https://gerrit.libreoffice.org/51544Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>
(cherry picked from commit 5b1442ec)
Reviewed-on: https://gerrit.libreoffice.org/51908Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>

ucb/source/ucp/file/filtask.cxx

@@ -65,7 +65,7 @@ TaskManager::endTask( sal_Int32 CommandId,
                       const OUString& aUncPath,
                       BaseContent* pContent)
 {
-    osl::MutexGuard aGuard( m_aMutex );
+    osl::ClearableMutexGuard aGuard( m_aMutex );
     TaskMap::iterator it = m_aTaskMap.find( CommandId );
     if( it == m_aTaskMap.end() )
         return;
@@ -79,6 +79,8 @@ TaskManager::endTask( sal_Int32 CommandId,
 
     m_aTaskMap.erase( it );
 
+    aGuard.clear();
+
     if( ErrorCode != TASKHANDLER_NO_ERROR )
         throw_handler(
             ErrorCode,