Update to tw cli v0.9.1

[adamrtalbot]

The tower-cli v0.9.1 includes a fix for the Google Batch executor problem seen (see seqeralabs/tower-cli#358 and seqeralabs/tower-cli#359).

We can now update the tower cli.

Changes:

• Update the Tower CLI to v0.9.1
• Add test for Tower CLI to export Google Batch environment