Share pause_server unit test between V2 & V2.1

This patch moves pause_server unit test from v3 directory to contrib
and makes it shared by V2 and V21.

PS. pause_server unit test cases was removed from admin actions unit
test case.

Partially implements blueprint v2-on-v3-api

Change-Id: Ideb30ec8501b4e98cb2ddaa4194bdf19002999ab
Merge "Share pause_server unit test between V2 & V2.1"