Fixed empty arg. for mysql connection.

test/module/net_sql.mysql.result

@@ -12,7 +12,7 @@ lua dump = function(v) return box.cjson.encode(v) end
 lua connect = {}
 ---
 ...
-lua for tk in string.gmatch(os.getenv('MYSQL'), '[^:]+') do table.insert(connect, tk) end
+lua for tk in string.gmatch(os.getenv('MYSQL')..':', '(.-):') do table.insert(connect, tk) end
 ---
 ...
 lua c = box.net.sql.connect('mysql', unpack(connect))

test/module/net_sql.mysql.skipcond

@@ -4,9 +4,6 @@ import os
 
 try:
     (host, port, user, password, db) = os.getenv('MYSQL').split(':')
-    for val in (host, port, user, password, db):
-        if not val.strip():
-            raise ValueError('Empty value')
     if not os.path.exists(os.path.join(self.args.builddir, 'src/module/mysql/mysql.so')):
         raise RuntimeError('No MySQL module found')
 except (RuntimeError, TypeError, NameError, AttributeError, ValueError):

test/module/net_sql.mysql.test

@@ -22,7 +22,7 @@ exec admin "lua c = box.net.sql.connect('mysql')"
 exec admin "lua dump = function(v) return box.cjson.encode(v) end"
 
 exec admin "lua connect = {}"
-exec admin "lua for tk in string.gmatch(os.getenv('MYSQL'), '[^:]+') do table.insert(connect, tk) end"
+exec admin "lua for tk in string.gmatch(os.getenv('MYSQL')..':', '(.-):') do table.insert(connect, tk) end"
 
 # mysql
 exec admin "lua c = box.net.sql.connect('mysql', unpack(connect))"