Revert "Switch to toybox hostname(1)."

This reverts commit b115b81095.

Reason for revert: http://b/123123255

Change-Id: I0f2bfebf1189fdc71e093538a8b228dd0e0b6946

ui/build/paths/config.go

@@ -90,6 +90,7 @@ var Configuration = map[string]PathConfig{
 	"grep":      Allowed,
 	"gzip":      Allowed,
 	"hexdump":   Allowed,
+	"hostname":  Allowed,
 	"jar":       Allowed,
 	"java":      Allowed,
 	"javap":     Allowed,
@@ -141,7 +142,6 @@ var Configuration = map[string]PathConfig{
 	"expr":      Toybox,
 	"head":      Toybox,
 	"getconf":   Toybox,
-	"hostname":  Toybox,
 	"id":        Toybox,
 	"ln":        Toybox,
 	"ls":        Toybox,