Fix running unit tests with coverage

The path to this repo is added to PYTHONPATH when the coverage flag is
specified so that the cinder entry points are discovered.

Change-Id: Ie33a63c6ecd443b900fa7bed3a1ec5b6bb0065e6
Closes-Bug: #1364347

run_tests.sh

@@ -132,6 +132,11 @@ function run_tests {
 
   if [ $coverage -eq 1 ]; then
     TESTRTESTS="$TESTRTESTS --coverage"
+    if [ -z "${PYTHONPATH:-}" ]; then
+        export PYTHONPATH=./
+    else
+        export PYTHONPATH=$PYTHONPATH:./
+    fi
   else
     TESTRTESTS="$TESTRTESTS"
   fi