sap_hostagent: Fix linting errors

[marcelmamula]

Fixes for ansible-lint that is updated as part of #1118

Changes

• replace module yum with package.
  • disable_gpg_check: true is not recognized by package module, but it is sent to underlying package manager. Tested on SLES with zypper.
• Replace all internal register variables with correct internal name __sap_hostagent_register_

Result

ansible-lint --version
ansible-lint 25.9.0 using ansible-core:2.19.2 ansible-compat:25.8.1 ruamel-yaml:0.18.14 ruamel-yaml-clib:0.2.12

ansible-lint roles/sap_hostagent/

# Before
Failed: 11 failure(s), 0 warning(s) in 11 files processed of 13 encountered.

# After
Passed: 0 failure(s), 0 warning(s) in 13 files processed of 15 encountered.

[berndfinger]

LGTM