Install as coreos-installer.legacy

For openshift/enhancements#210 I think
we will need at least some transitional period where RHCOS
ships both.  Even ignoring customers, the way our CI works
strongly encourages "ratcheting" changes in a compatible way,
i.e.:

- Introduce new thing, ship it
- Port consumers to new thing
- Remove old thing

And honestly I think this is a good model, because it forces
us to experience some of the pain that customers might feel here.

The basic idea here is:

- Install as `/usr/libexec/coreos-installer.legacy` so there's
  no chance of conflict with the real one
- Test for the presence of the "stamp file' we drop in our legacy initramfs
  so we know to defer to the real root's coreos-installer; see
  coreos/coreos-assembler#1389

Makefile

@@ -2,5 +2,5 @@ all:
 	@echo "(Nothing to do)"
 
 install:
-	install -D -t $(DESTDIR)/usr/libexec -m 0755 coreos-installer
+	install -D $(DESTDIR)/usr/libexec/coreos-installer.legacy -m 0755 coreos-installer
 	for x in dracut/*; do install -D -t $(DESTDIR)/usr/lib/dracut/modules.d/$$(basename $$x) $$x/*; done

dracut/30coreos-installer/coreos-installer-generator

@@ -4,6 +4,11 @@
 
 set -e
 
+# Verify we are in the legacy installer initramfs.
+if ! [ -f /etc/coreos-legacy-installer-initramfs ]; then
+  exit 0
+fi
+
 UNIT_DIR="${1:-/tmp}"
 
 cmdline=( $(</proc/cmdline) )

dracut/30coreos-installer/coreos-installer.service

@@ -6,7 +6,7 @@ OnFailureJobMode=isolate
 
 [Service]
 Type=simple
-ExecStart=/usr/libexec/coreos-installer
+ExecStart=/usr/libexec/coreos-installer.legacy
 # Perform reboot after install unless asked not to.
 ExecStop=/bin/sh -c 'test -f /tmp/skip_reboot || sleep 5 && reboot'
 #StandardInput=tty-force

dracut/30coreos-installer/module-setup.sh

@@ -48,7 +48,7 @@ install() {
         inst_multiple -o /lib/s390-tools/stage3.bin
     fi
 
-    inst_simple /usr/libexec/coreos-installer
+    inst_simple /usr/libexec/coreos-installer.legacy
 
     inst_simple "$moddir/coreos-installer-generator" \
         "$systemdutildir/system-generators/coreos-installer-generator"