The ServerMigrationSampleJsonTests functional tests set up
``self.api.microversion`` to 2.22 in its' setUp(), which use
sample files from non version dir.
For consistency, this commit makes these tests to use sample
files from versioned dir.
Change-Id: I9af2348cf7dba53e0fef4054bcedcd5b0c626f50
ghanshyam