Remove init and reset

[tatb-vmware]

This PR removes pxf init and pxf reset from the PXF bash script as a continuation of some of the removal done in https://github.com/greenplum-db/pxf/commit/a0fc43d0a8189b77f9e8edadf00a3b350f1987a2.

Change include:

• Replace pxf init with pxf register
• Remove logic and references to pxf init and pxf reset
• Remove testing for pxf init and pxf reset