Increases timeout for guest agent resize_fs

When the guest agent resizes the file system, it may take longer
than the AGENT_LOW_TIMEOUT and should use AGENT_HIGH_TIMEOUT to
ensure the resize has sufficient time to complete.

Change-Id: Ic3c030f60ca47d894eb25b83f05b63ef22d519f8
Closes-Bug: #1288766
Merge "Increases timeout for guest agent resize_fs"