run-tests: always set $COLUMNS, fix running tests under emacs shell

fix tests failure reported by Neal Becker.

tests/run-tests.py

@@ -785,6 +785,7 b' def main():'
     os.environ['TZ'] = 'GMT'
     os.environ["EMAIL"] = "Foo Bar <[e-mail]>"
     os.environ['CDPATH'] = ''
+    os.environ['COLUMNS'] = '80'
 
     global TESTDIR, HGTMP, INST, BINDIR, PYTHONDIR, COVERAGE_FILE
     TESTDIR = os.environ["TESTDIR"] = os.getcwd()

tests/test-churn

@@ -3,8 +3,6 b''
 echo "[extensions]" >> $HGRCPATH
 echo "churn=" >> $HGRCPATH
 
-COLUMNS=80; export COLUMNS
-
 echo % create test repository
 hg init repo
 cd repo

tests/test-patchbomb

@@ -12,8 +12,6 b' fixheaders()'
 echo "[extensions]" >> $HGRCPATH
 echo "patchbomb=" >> $HGRCPATH
 
-COLUMNS=80; export COLUMNS
-
 hg init t
 cd t
 echo a > a