(bug 47291) Make sure cloned Cite is cleared

The cloned Cite object in the ParserCloned hook must be cleared, even if
the clone occurs inside a <ref> or <references> tag. The simple way to
do this is to set mInCite and mInReferences to false before calling
clearState().

While Cite could probably use a major cleanup, let's fix this bug now
instead of waiting for someone to get around to it.

Bug: 47291
Change-Id: Id3e91c41dc33a703b5326961fd57e1fe8ac61f5b