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/cmd/pom2bp/pom2bp.go b/cmd/pom2bp/pom2bp.go
index a79c84f..a399b28 100644
--- a/cmd/pom2bp/pom2bp.go
+++ b/cmd/pom2bp/pom2bp.go
@@ -605,7 +605,7 @@
 	buf := &bytes.Buffer{}
 
 	fmt.Fprintln(buf, "// Automatically generated with:")
-	fmt.Fprintln(buf, "// pom2bp", strings.Join(proptools.ShellEscape(os.Args[1:]), " "))
+	fmt.Fprintln(buf, "// pom2bp", strings.Join(proptools.ShellEscapeList(os.Args[1:]), " "))
 
 	for _, pom := range poms {
 		var err error