init_host_server: correct getopts process

Sorry, #85 caused bug variable assignment went long, `PREVIEW_TARGET_URL="pool.dev"`
I fixed this problem. Please check the procedure `vegrant destroy -f && vagrant up` .
@mookjp sorry for my crabbed code..  conditional constructs can also take left parenthesis if it is needed. Thif left parenthesis is added for readability of the pattern.( Actually this snippet is copied from stackoverflow) 
Ref:) http://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html