Update hosting_civicrm_install() for D7

When installing to a fresh Aegir 3, enabling Hosting CiviCRM fails with

aegir@littlethunder:~$ drush @hostmaster dl hosting_civicrm
Project hosting_civicrm (7.x-3.1) downloaded to sites/all/modules/hosting_civicrm.                                                                                       [success]
Project hosting_civicrm contains 2 modules: hosting_civicrm_cron, hosting_civicrm.

aegir@littlethunder:~$ drush @hostmaster en hosting_civicrm hosting_civicrm_cron
The following extensions will be enabled: hosting_civicrm, hosting_civicrm_cron
Do you really want to continue? (y/n): y
WD php: DatabaseSchemaObjectDoesNotExistException: Cannot add field .hosting_site: table doesn't exist. in DatabaseSchema_mysql->addField() (line 325 of                 [error]
/var/aegir/hostmaster-7.x-3.0/includes/database/mysql/schema.inc).
Cannot modify header information - headers already sent by (output started at /var/aegir/.composer/vendor/drush/drush/includes/output.inc:38) bootstrap.inc:1232         [warning]
DatabaseSchemaObjectDoesNotExistException: Cannot add field .hosting_site: table doesn't exist. in DatabaseSchema_mysql->addField() (line 325 of /var/aegir/hostmaster-7.x-3.0/
includes/database/mysql/schema.inc).
Drush command terminated abnormally due to an unrecoverable error.                                                                                                       [error]

aegir@littlethunder:~$ drush @hostmaster en hosting_civicrm hosting_civicrm_cron
hosting_civicrm is already enabled.                                                                                                                                      [ok]
The following extensions will be enabled: hosting_civicrm_cron
Do you really want to continue? (y/n): y
WD php: DatabaseSchemaObjectDoesNotExistException: Cannot add field .hosting_site: table doesn't exist. in DatabaseSchema_mysql->addField() (line 325 of                 [error]
/var/aegir/hostmaster-7.x-3.0/includes/database/mysql/schema.inc).
Cannot modify header information - headers already sent by (output started at /var/aegir/.composer/vendor/drush/drush/includes/output.inc:38) bootstrap.inc:1232         [warning]
DatabaseSchemaObjectDoesNotExistException: Cannot add field .hosting_site: table doesn't exist. in DatabaseSchema_mysql->addField() (line 325 of /var/aegir/hostmaster-7.x-3.0/
includes/database/mysql/schema.inc).
Drush command terminated abnormally due to an unrecoverable error.