_lp_git_branch_color: simplify use of _lp_git_head_status
_lp_git_branch_color: simplify use of _lp_git_head_status

nojhan/liquidprompt,dtschan/liquidprompt,dpilone/liquidprompt,laurentbardin/liquidprompt,joshuarubin/dotfiles,dan-cleinmark/liquidprompt,alexprengere/liquidprompt,smadhueagle/liquidprompt,BobHood/liquidprompt,pkkolos/liquidprompt,joshuarubin/dotfiles,milouse/liquidprompt,joshuarubin/dotfiles,jaesivsm/liquidprompt,joshuarubin/dotfiles,tsbarnes/liquidprompt