promise check free disk/memory: fix 'attempt to write a readonly database'

Also set database connection timeout to 5 second

slapos/promise/check_computer_memory/__init__.py

@@ -17,7 +17,7 @@ from slapos.collect.db import Database
 def getMemoryInfo(database, time, date):
 
   memory_info = {}
-  database = Database(database)
+  database = Database(database, create=False, timeout=5)
   try:
     database.connect()
     query_result = database.select("computer", date, "memory_size", limit=1) 

slapos/promise/check_free_disk/__init__.py

@@ -16,7 +16,7 @@ from slapos.collect.db import Database
 
 def getFreeSpace(disk_partition, database, date, time):
 
-  database = Database(database)
+  database = Database(database, create=False, timeout=5)
   try:
     # fetch free disk space
     database.connect()