Use CVS's -f option if available (ignore user's ~/.cvsrc file)

A user's ~/.cvsrc file can change the basic behavior of CVS commands.
Therefore we should ignore it in order to ensure consistent results
from the test suite.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-cvs.sh

@@ -14,6 +14,9 @@ then
 	exit
 fi
 
+CVS="cvs -f"
+export CVS
+
 cvsps_version=`cvsps -h 2>&1 | sed -ne 's/cvsps version //p'`
 case "$cvsps_version" in
 2.1 | 2.2*)