units: remove service sysv_path variable and replace it by generic unit_path

UnitPath= is also writable via native units and may be used by generators
to clarify from which file a unit is generated. This patch also hooks up
the cryptsetup and fstab generators to set UnitPath= accordingly.

src/cryptsetup/cryptsetup-generator.c

@@ -115,6 +115,7 @@ static int create_disk(
                 "# Automatically generated by systemd-cryptsetup-generator\n\n"
                 "[Unit]\n"
                 "Description=Cryptography Setup for %%I\n"
+                "SourcePath=/etc/crypttab\n"
                 "Conflicts=umount.target\n"
                 "DefaultDependencies=no\n"
                 "BindTo=%s dev-mapper-%%i.device\n"
@@ -129,11 +130,9 @@ static int create_disk(
         if (password && (streq(password, "/dev/urandom") ||
                          streq(password, "/dev/random") ||
                          streq(password, "/dev/hw_random")))
-                fprintf(f,
-                        "After=systemd-random-seed-load.service\n");
+                fputs("After=systemd-random-seed-load.service\n", f);
         else
-                fprintf(f,
-                        "Before=local-fs.target\n");
+                fputs("Before=local-fs.target\n", f);
 
         fprintf(f,
                 "\n[Service]\n"