Migrate TestStampPattern to tempest client

Migrate TestStampPattern to tempest client. The test is currently
disabled in the gate, so this will be tested by adding a temp
patch on top removing the skip.

Partially-implements: bp:tempest-client-scenarios

Change-Id: I42524372ae64121f2e3b58f37b960f8d1bbc8b6a
Merge "Migrate TestStampPattern to tempest client"