Fix Get On Session errors

Fix Get On Session errors

'Get On Session' has different arguments and requirements but some of
the conversions from 'Get Request' to 'Get On Session' didn't take those
into account.

To prevent confusion that '=' is used for parameters when it is in fact
part of the URL path, specify 'url' a keyword argument, instead of
positional, and separate parameters into 'params' when possible.

Also, set 'odl-pretty-print' parameter for Phosphorus or later since it
is not available before the version. Accept any status code when there
is a separate step to check valid status codes.

Change-Id: Ibd41fe31090eb0406abd16e80b3e6168d424bc74
Signed-off-by: Sangwook Ha <sangwook.ha@verizon.com>