tests: fix debops_tests username rename.

.travis/debops_tests.sh

@@ -39,9 +39,9 @@ EOF
 cat > ansible/inventory/group_vars/debops_all_hosts.yml <<-EOF
 ansible_python_interpreter: /usr/bin/python2.7
 
-ansible_user: has-sudo-pubkey
+ansible_user: mitogen__has_sudo_pubkey
-ansible_become_pass: y
+ansible_become_pass: has_sudo_pubkey_password
-ansible_ssh_private_key_file: ${TRAVIS_BUILD_DIR}/tests/data/docker/has-sudo-pubkey.key
+ansible_ssh_private_key_file: ${TRAVIS_BUILD_DIR}/tests/data/docker/mitogen__has_sudo_pubkey.key
 
 # Speed up slow DH generation.
 dhparam__bits: ["128", "64"]