This commit also reverts 2 previous attempts to fix this very rare race issue spanning back to 2009

62ce8538 Patch from MOC
3a85348c FS-2302 mutex added around switch_xml_toxml()

The real problem was switch_xml_toxml_buf() was actually temporarily modifying the xml structure being searialized to make it appaer to be a root structure then serializing it and restoring the pointers.  This caused a non-threadsafe operation when some other thread was scanning the same xml structure.

This patch removes the modification and instead passes a new arg to switch_xml_toxml_r indicating to treat the structure as if it were a root structure.

This bug has been present since the induction of xml into FS.