test: do not hide test_emacs errors

test: do not hide test_emacs errors

Do not redirect test_emacs stderr to /dev/null.  Test_emacs uses
emacsclient(1) now and it does not print unwanted messages (like
those from `message') to stderr.  But it does print useful
errors, e.g. when emacs server connection fails, given expression
is not valid or undefined function is called.