webdav: fix locking in webdav_ucp::Content::getResourceType()

This commit cherry-picks 49a45422
for serf webdav version.

Change-Id: Ic5aba4fba8f8a2a521224b08865500dd932e85bf

ucb/source/ucp/webdav/webdavcontent.cxx

@@ -3410,7 +3410,17 @@ const Content::ResourceType & Content::getResourceType(
                     const uno::Reference< ucb::XCommandEnvironment >& xEnv )
     throw ( uno::Exception )
 {
-    return getResourceType( xEnv, m_xResAccess );
+    boost::scoped_ptr< DAVResourceAccess > xResAccess;
+    {
+        osl::MutexGuard aGuard( m_aMutex );
+        xResAccess.reset( new DAVResourceAccess( *m_xResAccess.get() ) );
+    }
+    const Content::ResourceType & ret = getResourceType( xEnv, xResAccess );
+    {
+        osl::Guard< osl::Mutex > aGuard( m_aMutex );
+        m_xResAccess.reset( new DAVResourceAccess( *xResAccess.get() ) );
+    }
+    return ret;
 }
 
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