revert the or_connection and dir_connection flags

They incorrectly summarized what the function was planning to do,
leading to wrong behavior like making an http request to an orport,
or making a begindir request to a dirport.

This change backs out some of the changes made in commit e72cbf7a, and
most of the changes made in commit ba6509e9.

This patch resolves bug 18625. There more changes I want to make
after this one, for code clarity.