update.py: fix layer exists-on-branch check

There was a logic error here - we were checking to see if the layer
directory existed before actually checking out the branch, which means
we were looking at the state of whatever branch was previously checked
out. Replace this with some validation of the last revision check and an
additional check for the directory after checking out the branch.

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>

0 files changed, 0 insertions, 0 deletions