Explicitly mark the session as modified on write operations

Fix #194

Signed-off-by: Byron Ruth <b@devel.io>
Merge pull request #195 from cbmi/issue-194

Explicitly mark the session as modified on write operations
2.4.0 Beta

Signed-off-by: Don Naegely <naegelyd@gmail.com>
Require Avocado 2.4 branch

Signed-off-by: Don Naegely <naegelyd@gmail.com>