Not enable the rustls feature by default for sqlx

[guenhter]

DB's like sqlite not need the tls feature with sqlx at all. When cross compiling e.g. to i586, ring is not supported and therefore the db-pool cannot be used because the rustls feature is turned on by default even though not needed.

[guenhter]

@SergioBenitez Is there anything else I should do to make this PR move along faster? The issue really hinders me and I have to patch all other libs too which I use and depend on rocket to make it working with cargo and this version of the PR.