tests: use common function to check for file existence

This addresses issue with "docker cp" in some systems.

tests/radius-test

@@ -102,18 +102,7 @@ if test $? != 0;then
 	stop
 fi
 
-$DOCKER exec -i -t $IMAGE_NAME occtl show users
-$DOCKER exec -i -t $IMAGE_NAME occtl show user test >out$TMP 2>&1
-
-grep "Username" out$TMP
-if test $? != 0;then
-	cat out$TMP
-	kill $PID
-	echo "could not find user information"
-	stop
-fi
-
-rm -f out$TMP
+retrieve_user_info test
 
 # There is an issue in nuttcp that makes it crash under docker if
 # /proc/sys/net/ipv4/tcp_adv_win_scale does not exist.
@@ -140,16 +129,11 @@ kill -INT $PID
 
 sleep 4
 
-TMPDIR=radius-$TMP
-mkdir -p $TMPDIR
-#check whether /tmp/disconnect/ok was created
-rm -f $TMPDIR/not-ok
-$DOCKER cp $IMAGE_NAME:/tmp/disconnect/not-ok $TMPDIR/
-if test -f $TMPDIR/not-ok;then
-	echo "There was an issue getting stats"
+check_for_file /tmp/disconnect/not-ok
+if test $? = 0;then
+	echo "There was an issue"
 	stop
 fi
-rm -f $TMPDIR/not-ok
 
 rm -f $TMPDIR/stats
 
@@ -163,15 +147,10 @@ if test -z "$OCTETS" || test "$OCTETS" = 0;then
 	stop
 fi
 
-rm -f $TMPDIR/ok
-$DOCKER cp $IMAGE_NAME:/tmp/disconnect/ok $TMPDIR/
-if ! test -f $TMPDIR/ok;then
-	echo "Don't know if stats were received"
-	ret=77
-else
-	echo -n "stats: "
-	echo `cat $TMPDIR/ok`
-	rm -rf $TMPDIR/
+check_for_file /tmp/disconnect/ok
+if test $? != 0;then
+	echo "There was an issue getting stats"
+	stop
 fi
 
 ret=0