Issue type:

[x] bug report

Database system/driver:

[x] mongodb

TypeORM version:

[x] the bug is reproduced starting from 0.2.25 (0.2.24 is OK)

Steps to reproduce or a small repository showing the problem:

Mongo DB URL without query params is OK
TYPEORM_URL = mongodb://127.0.0.1:27017/testing
the database called testing will be created

Mongo DB URL with query params (bug)
TYPEORM_URL = mongodb://127.0.0.1:27017/testing?readPreference=primary&appName=xxx
the database called testing?readPreference=primary&appName=xxx will be created

The bug appeared in this commit (src/connection/Connection.ts:538):
ed75d59#diff-9ada25e7bb500fdf98eeb214f7c94e9aR538