Add filtering by service to hosts list command

This commit adds --service-name option to host-list command allowing
user to filter hosts by service.

DocImpact
Closes-Bug: 1224763
Change-Id: Ic67deb3af7ddbe23c14fa38ae180d43ab484b78f
Merge "Add filtering by service to hosts list command"
Updated from global requirements

Change-Id: I6c2fb676276746719e982d42857e1d03a502d886
Update requirements.txt to include keystoneclient

Keystone client is required by nova client and needs to be in
requirements.txt. It is currently in test-requirements.txt but also
needs to be in install requirements.

Change Ief6cd7e752fd8c9e9157364f99e270da7faff074 introduced the
requirement for keystone client.

Change-Id: I91f58810e0511d0d4acc5bba0c0e946edf247896
Closes-Bug: 1358675
Merge "Updated from global requirements"