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/java/dexpreopt_bootjars.go b/java/dexpreopt_bootjars.go
index ca68832..64de21a 100644
--- a/java/dexpreopt_bootjars.go
+++ b/java/dexpreopt_bootjars.go
@@ -281,7 +281,7 @@
 		cmd.Flag(extraFlags)
 	}
 
-	cmd.Textf(`|| ( echo %s ; false )`, proptools.ShellEscape([]string{failureMessage})[0])
+	cmd.Textf(`|| ( echo %s ; false )`, proptools.ShellEscape(failureMessage))
 
 	installDir := filepath.Join("/system/framework", arch.String())
 	vdexInstallDir := filepath.Join("/system/framework")