Change default for update_grub_to_grub_2 from true to false. (#98)

* Change default for update_grub_to_grub_2 from true to false.

* Add changelog for default_grub_upgrade_to_false.

changelogs/fragments/default_grub_upgrade_to_false.yml

@@ -0,0 +1,4 @@
+---
+minor_changes:
+  - Change default value for update_grub_to_grub_2 from true to false.  Grub will not be upgraded by default.
+...

roles/upgrade/README.md

@@ -12,6 +12,7 @@ The `upgrade` role is used to kick off the Leapp OS upgrade on the target host.
 | set_crypto_policies     | true                  | Boolean to define if system-wide cryptographic policies should be set after the OS upgrade |
 | crypto_policy           | "DEFAULT"             | System-wide cryptographic to set, e.g., "FUTURE", "DEFAULT:SHA1", etc. Refer to the crypto-policies (7) man page for more information. |
 | post_reboot_delay       | 120                   | Optional integer to pass to the reboot post_reboot_delay option. |
+| update_grub_to_grub_2   | false                 | Boolean to control whether grub gets upgraded to grub 2 in post RHEL 6 to 7 upgrade. |
 
 ## Example playbook
 

roles/upgrade/defaults/main.yml

@@ -34,7 +34,7 @@ crypto_policy: DEFAULT
 # crypto_policy: DEFAULT:SHA1
 
 # Whether or not to update from legacy grub to grub2 in post-upgrade steps from RHEL 6 -> 7.
-update_grub_to_grub_2: true
+update_grub_to_grub_2: false
 
 # Used by grub to grub2 upgrade in RHEL 6 to 7 post upgrade, and RHEL 7 to 8 post upgrade.
 # For grub to grub2 upgrade, if grub_boot_device is not defined, the parent device of /boot