Ajs fix ecred bug

[aschroed]

Make request to get_upload_creds to use datastore=database to avoid timing issues that was preventing multiple extra_file uploads.

[coveralls]

coverage: 83.173% (-0.01%) from 83.187%
when pulling cad104b on ajs_fix_ecred_bug
into d80a7db on master.

[coveralls]

coverage: 83.173% (-0.01%) from 83.187%
when pulling cad104b on ajs_fix_ecred_bug
into d80a7db on master.

[willronchetti]

Let's see if this fix alone is enough, it may be worth scanning the file for other instances and converting it to database calls elsewhere as well

[RahiNav]

Tested using dummy files - 2 fastq, 2 compressed tsv with index files. Uploaded at the same time. All were successfully uploaded.