Switch to toybox hostname(1).

Test: treehugger
Change-Id: Ibf89209befc8564b308c4b26bf08cef721938099
diff --git a/ui/build/paths/config.go b/ui/build/paths/config.go
index 1c0ee34..5344e3f 100644
--- a/ui/build/paths/config.go
+++ b/ui/build/paths/config.go
@@ -90,7 +90,6 @@
 	"grep":      Allowed,
 	"gzip":      Allowed,
 	"hexdump":   Allowed,
-	"hostname":  Allowed,
 	"jar":       Allowed,
 	"java":      Allowed,
 	"javap":     Allowed,
@@ -146,6 +145,7 @@
 	"expr":      Toybox,
 	"head":      Toybox,
 	"getconf":   Toybox,
+	"hostname":  Toybox,
 	"id":        Toybox,
 	"ln":        Toybox,
 	"ls":        Toybox,