s3gw: fix sqlite version (maybe others?) on Dockerfile

[jecluis]

Fixing versions in the Dockerfile will allow us to upgrade packages without them affecting already released versions, or on-going releases.

This comes about via #723 where we kind of want to upgrade sqlite, but because we're not fixing the version in the Dockerfile, upgrading it right now in https://build.opensuse.org/project/show/filesystems:ceph:s3gw would affect the on-going release effort, upgrading a major library right from under us while the release process is on-going.

Additionally, by not fixing releases in the Dockerfile, we fall into the trap of having, e.g., v0.21.0 on sqlite X.Y.A, and then all versions post v0.21.0, including v0.21.1, v0.21.2, etc (should they exist), on a future version of sqlite X.Y.B (or something similar).