azure: test: silence termination message when killing git-daemon(1)

In order to properly tear down the test environment, we will kill
git-daemon(1) if we've exercised it. As git-daemon(1) is spawned as a
background process, it is still owned by the shell and thus killing it
later on will print a termination message to the shell's stderr, causing
Azure to report it as an error.

Fix this by disowning the background process.

azure-pipelines/test.sh

@@ -81,6 +81,7 @@ if [ -z "$SKIP_GITDAEMON_TESTS" ]; then
 	git init --bare "${GITDAEMON_DIR}/test.git"
 	git daemon --listen=localhost --export-all --enable=receive-pack --base-path="${GITDAEMON_DIR}" "${GITDAEMON_DIR}" 2>/dev/null &
 	GITDAEMON_PID=$!
+	disown $GITDAEMON_PID
 fi
 
 if [ -z "$SKIP_PROXY_TESTS" ]; then