Fix Travis-CI

[jholtom-ciena]

Changes to enable test-suite to complete successfully, and enable fresh release to be made.
Most changes for the fdw-pg image:

• Replace generic postgres:10 docker image with last specific version using python2.7
• Fetch and install corresponding postgresql-server-dev-10, postgresql-plpython-10 packages plus dependencies libpq5, and libpq-dev from postgresql.org archives
• Install libfaketime, and apply settings which will import and apply only when postgres is doing first-time initialisation. (Need a summer date, so that PST/PDT is UTC-7, per the expected outputs for pg_regress)

Small changes for the fdw-neo4j image:

• Use vanilla 'su', given loss of 'su-exec' now Neo4J no-longer uses Alpine Linux

[sim51]

@jholtom-ciena Thanks a lot for your contribution, it's perfect !