Fix find_network_host for test with file injection
Fix find_network_host for test with file injection

-make function find_network_host as a global
-fix functions where used find_network_host

Change-Id: Ife8ab2c624071cbe93383bd25b88ffd84f3fbdf1
Closes-bug: #1449578

eayunstack/fuel-ostf,eayunstack/fuel-ostf,stackforge/fuel-ostf,mcloudv/fuel-ostf,stackforge/fuel-ostf,mcloudv/fuel-ostf