testing/betula: add curl to checkdepends

It is used by the test-web.sh script, and used to be
a dependency of abuild before it was removed in
20c1bf07870c961d1b506e6d6861329910e2f1df

testing/betula/APKBUILD

@@ -8,6 +8,7 @@ arch="all"
 license="AGPL-3.0-only"
 options="net" # go modules
 makedepends="go sqlite-dev"
+checkdepends="curl"
 subpackages="$pkgname-openrc"
 install="$pkgname.pre-install"
 builddir="$srcdir/$pkgname-v$pkgver"
@@ -28,6 +29,11 @@ build() {
 
 check() {
 	./test-web.sh
+	local ret=$?
+
+	# Cleanup so we don't hang CI
+	killall -q betula
+	return $ret
 }
 
 package() {