tmpfiles.sh: do not use install

install is in /usr which causes problems if /usr is not mounted.
Instead, checkpath and "mkdir -p" can do everything required and are
both available before /usr is mounted.
Since checkpath also handles selinux labels correctly,
_restorecon after is not required.

X-Gentoo-Bug: 503408
X-Gentoo-Bug-URL: https://bugs.gentoo.org/show_bug.cgi?id=503408