Replace *Escape with *EscapeList

Follow the change to blueprint to make *Escape take and return a string
and add *EscapeList that take and return slices of strings.  Fix up
a few places that were unnecessarily converting a string to a slice
and back to a string.

Test: m nothing
Change-Id: I3fa87de175522205f36544ef76aa2f04aef1b936
diff --git a/tradefed/autogen.go b/tradefed/autogen.go
index 6d9c200..da5dabe 100644
--- a/tradefed/autogen.go
+++ b/tradefed/autogen.go
@@ -67,7 +67,7 @@
 	}
 	sort.Strings(options)
 	extraOptions := strings.Join(options, "\n        ")
-	extraOptions = proptools.NinjaAndShellEscape([]string{extraOptions})[0]
+	extraOptions = proptools.NinjaAndShellEscape(extraOptions)
 
 	ctx.Build(pctx, android.BuildParams{
 		Rule:        autogenTestConfig,