Upgrade dracut module: Update /usr mounting solution

Originally we had implemented our own mount_usr.sh script, which
took care about mounting the /usr when it is present on separate
partition / mountpoint. It took care also about LVM activation.

However, it has been problematic in various cases (e.g. when device
needed more time for initialisation - e.g. when connected using FC).
Let's use instead existing system solutions, starting
the upgrade.target after initrd-fs.target (instead of just
basic.target).

jira: RHEL-3344

repos/system_upgrade/common/actors/commonleappdracutmodules/files/dracut/85sys-upgrade-redhat/module-setup.sh

@@ -102,7 +102,6 @@ install() {
     inst_binary grep
 
     # script to actually run the upgrader binary
-    inst_hook upgrade 49 "$_moddir/mount_usr.sh"
     inst_hook upgrade 50 "$_moddir/do-upgrade.sh"
 
     #NOTE: some clean up?.. ideally, everything should be inside the leapp*

repos/system_upgrade/common/actors/commonleappdracutmodules/files/dracut/90sys-upgrade/upgrade.target

@@ -2,7 +2,7 @@
 Description=System Upgrade
 Documentation=man:upgrade.target(7)
 # ##sysinit.target sockets.target initrd-root-fs.target initrd-root-device.target initrd-fs.target
-Wants=initrd-root-fs.target initrd-root-device.target initrd-fs.target initrd-usr-fs.target
+Wants=initrd-root-fs.target initrd-root-device.target initrd-fs.target initrd-usr-fs.target initrd-parse-etc.service
 Requires=basic.target sysroot.mount
-After=basic.target sysroot.mount
+After=basic.target sysroot.mount  initrd-fs.target
 AllowIsolate=yes