Horizon has removed Saharaclient and Troveclient from its dependencies,
so, remove their code from Manila-UI too.
Latest release of Manilaclient v1.6.0 broke possibility to import
deprecated v1 API modules having b_u_g 1535692. So, change usage of
manilaclient in the way when we do not hit that bug.
Change-Id: I907502a6dcb9ff8521935428bbb34b930b134553
Closes-Bug: #1535657