Removes Unneeded mysql::server Dependency

Previously, the heat::db::mysql class contained a dependency on
mysql::server. This dependency is unneeded since mysql::db requires
mysql::config, which depends on mysql::server. Additionally, the
mysql::server dependency causes MYSQL HA installations such as
Galera to fail. Lastly, this aligns the class more closely with
the other [OPENSTACK_SERVICE]::db::mysql classes.

Change-Id: Ie6c4d3c8aaa531502bc5b9cd66a547f1f506385f

manifests/db/mysql.pp

@@ -34,7 +34,6 @@ class heat::db::mysql(
 
   validate_string($password)
 
-  Class['mysql::server'] -> Class['heat::db::mysql']
   Class['heat::db::mysql'] -> Exec<| title == 'heat-manage db_sync' |>
   Mysql::Db[$dbname] ~> Exec<| title == 'heat-manage db_sync' |>
 

spec/classes/heat_db_mysql_spec.rb

@@ -5,10 +5,6 @@ describe 'heat::db::mysql' do
     { :osfamily => 'RedHat' }
   end
 
-  let :pre_condition do
-    'include mysql::server'
-  end
-
   let :params do
     { :password  => 's3cr3t',
       :dbname    => 'heat',