Backport VTS fixes to previous test versions

Network scan check periodicity only if scan type is PERIODIC.
Fix MCC/MNC checks to handle null strings.

Test: atest VTS
Bug: 259674407
Change-Id: I77e0706f413ce9defb174f00ee145dcc01f5d780
Merged-In: I77e0706f413ce9defb174f00ee145dcc01f5d780
(cherry picked from commit 8ab8f0d1d81a0037d1ba0a404d7da491f1b1466f)
4 files changed