psutils: Move functions from updater to utils

Move common, utility functions from updater.*pp to utils.*pp. This will
enable those functions to be used by other command line options in the
psutils

psutils: Move functions from updater to utils

Move common, utility functions from updater.*pp to utils.*pp. This will
enable those functions to be used by other command line options in the
psutils tool.

Modify --get-version and --get-model to use the new utility functions.

Also update --get-version to provide a single getVersion() function that
handles the existence of the psu.json file as a low-level implementation
detail.

Tested:
* Verified all automated tests run successfully
* Verified --get-version still works
* With psu.json file
* Without psu.json file
* Verified --get-model still works
* With psu.json file
* Without psu.json file
* Verified --update still gets correct device path, device name, and I2C
bus/address from functions that moved to utils.*pp
* The complete test plan is available at
https://gist.github.com/smccarney/c049e24655d32e22cab9d521d145774a

Change-Id: I51ceca10957dc9a924d0d7516dc29632a6ed82d3
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>

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