Explicitly enable all our database backends in CI

BDBD, LMDB and SQLite were already implicitly enabled via build
dependencies, but NDB build has not been enabled at all.
Came up when discussing read-only BDB in #980.

ci/Dockerfile

@@ -56,6 +56,10 @@ RUN ./configure \
   --with-acl \
   --with-lua \
   --with-audit \
+  --enable-bdb \
+  --enable-ndb \
+  --enable-lmdb \
+  --enable-sqlite \
   --enable-python \
   --enable-silent-rules \
   --enable-werror