Disable fallocate and set max_file_size to default

- We used to set max_file_size to 10000 to get the functional tests
  passing on devstack but this was the wrong way. We are now disabling
  fallocate like done in saio to get the large objects test passing.
- Fixes bug 1201077.

Change-Id: I33058352f5abfb06f2a992890cbc7339cedc0ad3
Fix vm_test_mode

- It was previously incorrectly generated.
- Fixes bug 1201694.

Change-Id: I802bbd0ced8f12064189db7d707fbb6ca09113bb
Merge "Fix vm_test_mode"
Merge "Disable fallocate and set max_file_size to default"