import: don't create sparse tar archives

Sparse archives are good for files like utmp/wtmp and journals, but it
is still expenseive in having to read the files twice to archive them.
Additionally there is a supportability issue as GNU sparse archives are
not supported by many archive libraries and tooling.

src/import/import-common.c

@@ -210,7 +210,7 @@ int import_fork_tar_c(const char *path, pid_t *ret) {
                 if (r < 0)
                         log_error_errno(r, "Failed to drop capabilities, ignoring: %m");
 
-                execlp("tar", "tar", "--sparse", "-C", path, "-c", ".", NULL);
+                execlp("tar", "tar", "-C", path, "-c", ".", NULL);
                 log_error_errno(errno, "Failed to execute tar: %m");
                 _exit(EXIT_FAILURE);
         }