Move xml_free_parser out of destructor.

Move xml_free_parser out of destructor.

Attempt to reduce error log spam. I'm not sure about the exact
cause of this error, nor have I really reproduced locally, so
I don't know if this will help, but getting it out of destructor
seems like a good idea.

I also do not know if calling xml_free_parser is really needed
(Would php automatically destroy parser during garbage collection?)

Bug: T89532
Change-Id: I5709b6cf26cf4a9032a79d2b5f48ed3b4238eaee