execute: drop DissectImageFlags parameter from namespace_setup()

The function already has a ridiculous amount of paramaters, let's drop
one that is either not used at all or has a constant value and let's
pick it internally.

src/core/execute.c

@@ -3247,7 +3247,6 @@ static int apply_mount_namespace(
                             propagate_dir,
                             incoming_dir,
                             root_dir || root_image ? params->notify_socket : NULL,
-                            DISSECT_IMAGE_DISCARD_ON_LOOP|DISSECT_IMAGE_RELAX_VAR_CHECK|DISSECT_IMAGE_FSCK|DISSECT_IMAGE_USR_NO_ROOT,
                             error_path);
 
         /* If we couldn't set up the namespace this is probably due to a missing capability. setup_namespace() reports

src/core/namespace.c

@@ -1802,7 +1802,6 @@ int setup_namespace(
                 const char *propagate_dir,
                 const char *incoming_dir,
                 const char *notify_socket,
-                DissectImageFlags dissect_image_flags,
                 char **error_path) {
 
         _cleanup_(loop_device_unrefp) LoopDevice *loop_device = NULL;
@@ -1813,6 +1812,13 @@ int setup_namespace(
         MountEntry *m = NULL, *mounts = NULL;
         bool require_prefix = false, setup_propagate = false;
         const char *root, *extension_dir = "/run/systemd/unit-extensions";
+        DissectImageFlags dissect_image_flags =
+                DISSECT_IMAGE_GENERIC_ROOT |
+                DISSECT_IMAGE_REQUIRE_ROOT |
+                DISSECT_IMAGE_DISCARD_ON_LOOP |
+                DISSECT_IMAGE_RELAX_VAR_CHECK |
+                DISSECT_IMAGE_FSCK |
+                DISSECT_IMAGE_USR_NO_ROOT;
         size_t n_mounts;
         int r;
 
@@ -1825,8 +1831,6 @@ int setup_namespace(
                 mount_flags = MS_SHARED;
 
         if (root_image) {
-                dissect_image_flags |= DISSECT_IMAGE_GENERIC_ROOT | DISSECT_IMAGE_REQUIRE_ROOT;
-
                 /* Make the whole image read-only if we can determine that we only access it in a read-only fashion. */
                 if (root_read_only(read_only_paths,
                                    ns_info->protect_system) &&

src/core/namespace.h

@@ -143,7 +143,6 @@ int setup_namespace(
                 const char *propagate_dir,
                 const char *incoming_dir,
                 const char *notify_socket,
-                DissectImageFlags dissected_image_flags,
                 char **error_path);
 
 #define RUN_SYSTEMD_EMPTY "/run/systemd/empty"

src/test/test-namespace.c

@@ -187,7 +187,6 @@ static void test_protect_kernel_logs(void) {
                                     NULL,
                                     NULL,
                                     NULL,
-                                    0,
                                     NULL);
                 assert_se(r == 0);
 

src/test/test-ns.c

@@ -107,7 +107,6 @@ int main(int argc, char *argv[]) {
                             NULL,
                             NULL,
                             NULL,
-                            0,
                             NULL);
         if (r < 0) {
                 log_error_errno(r, "Failed to set up namespace: %m");