test-apt-update-reporting: Make more use of framework

Use msgtest and testsuccess with a function instead of failing
with a simple exit 1. This looks nicer.

Gbp-Dch: ignore

test/integration/test-apt-update-reporting

@@ -16,16 +16,20 @@ changetowebserver
 
 aptget update -o Debug::Acquire::Progress=1 2>progress.log >ignore.out
 
-prev_percent=0.0
-while read line; do
-    percent="$(echo "$line"|cut -b2-6)"
-    # need to cut the decimal point and digits because sh can not do
-    # float compare
-    if [ "${percent%%.*}" -lt "${prev_percent%%.*}" ]; then
-        echo "progress goes backwards"
-        cat progress.log
-        exit 1
-    fi
-    prev_percent="$percent"
-done < progress.log
+has_progress() {
+    prev_percent=0.0
+    while read line; do
+        percent="$(echo "$line"|cut -b2-6)"
+        # need to cut the decimal point and digits because sh can not do
+        # float compare
+        if [ "${percent%%.*}" -lt "${prev_percent%%.*}" ]; then
+            cat progress.log
+            return 1
+        fi
+        prev_percent="$percent"
+    done < progress.log
+    return 0
+}
 
+msgtest "Testing that progress does not go backward"
+testsuccess --nomsg has_progress