Make test_show_host_detail work with multi host installation

Get the host detail only if the host is compute host
and run the tests for all the compute host not just
for the first one.

Closes-Bug: #1230000

Change-Id: I1830e6071c09d1e751048d74bd828d0eeac282f8
(cherry-picked from 699183617eb99449ae778fdd35475d551ab68b15)
Merge "Make test_show_host_detail work with multi host installation" into stable/havana