Trebuchet : Default workspace improvements

Ported from cm-10.2

Adds support for fallback in default_workspace

Change-Id: I2590ae2d5e3c1b6124061581b9ffa206d611c608
Trebuchet : Port default workspace

Port default workspace from cm-10.2

Change-Id: Ia817baef17e2edc8c384d215f2d2cba07dd21be9