This commit also reverts 2 previous attempts to fix this very rare race issue spanning back to 2009
62ce853897 Patch from MOC
3a85348cdf 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.