Do not create OpenApiObject twice

Do not create OpenApiObject twice

Refactor the getMountPointApi method to prevent the creation
of two OpenApiObject instances. Currently,
this duplication occurs because the method is responsible for both
creating the required paths and generating the OpenApiObject.

To improve the code, separate these two functions and use only
the method that creates the data-store paths. This change will make
the code cleaner and more efficient, and help to avoid any potential
issues caused by duplicate objects.

JIRA: NETCONF-1007
Change-Id: I5ff38b706ce34c270f43fd4cf00a98efcbdaf888
Signed-off-by: Peter Suna <peter.suna@pantheon.tech>
Signed-off-by: Ivan Hrasko <ivan.hrasko@pantheon.tech>