sysv-generator: initialize LookupPaths just once

With debugging on, sysv-generator would print the full set of
lookup paths for *every* sysv script.

While at it, pass LookupPaths as a pointer in sysv-generator,
and constify it everywhere.

src/shared/install.h

@@ -23,6 +23,7 @@
 
 #include "hashmap.h"
 #include "unit-name.h"
+#include "path-lookup.h"
 
 typedef enum UnitFileScope {
         UNIT_FILE_SYSTEM,
@@ -98,7 +99,15 @@ int unit_file_set_default(UnitFileScope scope, const char *root_dir, const char
 int unit_file_get_default(UnitFileScope scope, const char *root_dir, char **name);
 int unit_file_add_dependency(UnitFileScope scope, bool runtime, const char *root_dir, char **files, char *target, UnitDependency dep, bool force, UnitFileChange **changes, unsigned *n_changes);
 
-UnitFileState unit_file_get_state(UnitFileScope scope, const char *root_dir, const char *filename);
+UnitFileState unit_file_lookup_state(
+                UnitFileScope scope,
+                const char *root_dir,
+                const LookupPaths *paths,
+                const char *name);
+UnitFileState unit_file_get_state(
+                UnitFileScope scope,
+                const char *root_dir,
+                const char *filename);
 
 int unit_file_get_list(UnitFileScope scope, const char *root_dir, Hashmap *h);