build-unit-test: fetch libldap2-dev

phosphor-ldap-config requires libldap2-dev headers and libs.

Change-Id: I67b6429e3c219e4e93d323b80fd567d0cf9d4bf8
Signed-off-by: Deepak Kodihalli <dkodihal@in.ibm.com>
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/build-unit-test-docker.sh b/build-unit-test-docker.sh
index 499c17c..28b8c23 100755
--- a/build-unit-test-docker.sh
+++ b/build-unit-test-docker.sh
@@ -147,7 +147,8 @@
     libpam0g-dev \
     xxd \
     libi2c-dev \
-    wget
+    wget \
+    libldap2-dev
 
 RUN pip install inflection
 RUN pip install pycodestyle