Cleaned up framework_base class method implementations.
Cleaned up framework_base class method implementations.

Two routines had unreachable lines (code lines after a raise). These
were removed. Also made slice_name_to_urn conform to other base class
methods now that it is implemented in each framework-specific class.

tcmitchell/geni-tools,GENI-NSF/gram,ahelsing/geni-tools,GENI-NSF/gram,GENI-NSF/gram,plantigrade/geni-tools,plantigrade/geni-tools,tcmitchell/geni-tools,ahelsing/geni-tools