Add MYSQL_CONF env var to mariadb, same as mysql, allowing mariadb

plugin users to easily override things. Also, add a commented out 'port'
line in each my.cnf, since this is the most likely change needed.

Author: jefft

plugins/mariadb.json

@@ -7,7 +7,8 @@
     "MYSQL_HOME": "{{ .Virtenv }}/run",
     "MYSQL_DATADIR": "{{ .Virtenv }}/data",
     "MYSQL_UNIX_PORT": "{{ .Virtenv }}/run/mysql.sock",
-    "MYSQL_PID_FILE": "{{ .Virtenv }}/run/mysql.pid"
+    "MYSQL_PID_FILE": "{{ .Virtenv }}/run/mysql.pid",
+    "MYSQL_CONF": "{{ .DevboxDir }}/my.cnf"
   },
   "create_files": {
     "{{ .Virtenv }}/run": "",

plugins/mariadb/my.cnf

@@ -1,4 +1,6 @@
 # MySQL configuration file
 
-[mariadb]
+[mariadbd]
+# Change this port if 3360 is already used
+#port = 3360
 log_error=mysql.log

plugins/mysql/my.cnf

@@ -2,3 +2,5 @@
 
 # [mysqld]
 # skip-log-bin
+# Change this port if 3360 is already used
+#port = 3360