Continuing 2.3 weirdness

[Robert J. Hansen]

> I make different observations (using self-compiled gpg installed to /opt/
> gnupg/master with a non-standard GNUPGHOME):

It turns out the source of the trouble was systemd, which was starting 
gpg-agent on demand, and was forcing it to use /usr/bin/gpg-agent. 
Setting a user override file fixed the behavior.

Really annoying to hunt down, though.  My thanks to Phil Pennock for 
helping me debug this.