fixes #56: pillar lookup.server value is ignored

mysql/client.sls

 {% from "mysql/defaults.yaml" import rawmap with context %}
-{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:server:lookup')) %}
+{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:lookup')) %}
 
 mysql:
   pkg.installed:

mysql/database.sls

 {% from "mysql/defaults.yaml" import rawmap with context %}
-{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:server:lookup')) %}
+{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:lookup')) %}
 
 {% set mysql_root_pass = salt['pillar.get']('mysql:server:root_password', salt['grains.get']('server_id')) %}
 {% set db_states = [] %}

mysql/server.sls

 {% from "mysql/defaults.yaml" import rawmap with context %}
-{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:server:lookup')) %}
+{%- set mysql = salt['grains.filter_by'](rawmap, grain='os', merge=salt['pillar.get']('mysql:lookup')) %}
 
 {% set os = salt['grains.get']('os', None) %}
 {% set os_family = salt['grains.get']('os_family', None) %}