bnc#883684: Better fix for this.

Instead of making all chart objects exempt from unloading, check each OLE
object on whether or not it already has its persistent storage created.
If not, don't unload it else it would have nothing to load back from once
unloaded.

(cherry picked from commit a0bd5587a5ac62974bdb10731d3fd21584521a72)

Conflicts:
	svx/source/svdraw/svdetc.cxx

Change-Id: I2312e86c9376d3699ef4aa1e0cf2f4c04f706c1e
Reviewed-on: https://gerrit.libreoffice.org/10237
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>