mongodb default options removed.

[fatihsucu]

Fixes #2579

[coveralls]

Coverage increased (+0.006%) to 90.284% when pulling 772bcb8 on fatihsucu:hotfix_for_pymongo into 0cfacb7 on celery:master.

[thedrow]

I think that this code should branch based on PyMongo's version.
If it's version 3 and above don't set the defaults.

[PMickael]

I think, It would be better to treat the exception !

[ionelmc]

Turns out max_pool_size was renamed to maxPoolSize. The other option is removed in 3.0 (it had something to do with read-after-write preference, see https://github.com/mongodb/mongo-python-driver/blob/master/doc/changelog.rst#classpymongomongo_clientmongoclient-changes )

@fatihsucu will you update the PR to have version check and only set maxPoolSize on 3.0 ?

[fatihsucu]

Yes, i will @ionelmc

[coveralls]

Coverage decreased (-0.01%) to 90.27% when pulling e53e170 on fatihsucu:hotfix_for_pymongo into 0cfacb7 on celery:master.

[coveralls]

Coverage decreased (-0.01%) to 90.27% when pulling c0b366d on fatihsucu:hotfix_for_pymongo into 0cfacb7 on celery:master.

[PMickael]

Great thanks.
Add you're name to contributor if you want.

[fatihsucu]

Thanks for comments and advice. It would be great.

[ask]

Wow, these mongo folks sure love pointless and backward incompatible changes ;)

[ask]

Also applied to 3.1