Add vars to devtest_variables.sh

Adds the DEPLOY_* and NODE_CNT vars to devtest_variables.sh, and makes
sure they are exported. Exporting them will allow them to be saved by
write-tripleorc, and their values are important enough to be saved and
reused via the tripleorc file.

Change-Id: I043ced247827b10455826c413775be3ddc4d3473
Merge "Add vars to devtest_variables.sh"