[autotest] Add two helper functions to install packages.

Server-side test should call these two functions to install required packages.
Ideally, tests will not need to deploy packages to site-packages for test to
run.

BUG=chromium:453614
TEST=site_utils/lxc_functional_test.py

Change-Id: I9ade9e1a804897a32cebac36836367feda13a24b
Reviewed-on: https://chromium-review.googlesource.com/268437
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
diff --git a/site_utils/lxc_functional_test.py b/site_utils/lxc_functional_test.py
index e3a8436..b8dc141 100644
--- a/site_utils/lxc_functional_test.py
+++ b/site_utils/lxc_functional_test.py
@@ -178,6 +178,16 @@
         raise Exception('Failed to read status.log in container.')
 
 
+def test_package_install(container):
+    """Test installing package in container.
+
+    @param container: The test container.
+    """
+    container.attach_run('sudo apt-get update -y')
+    container.attach_run('sudo apt-get install python-pip -y')
+    container.attach_run('sudo pip install selenium')
+
+
 def parse_options():
     """Parse command line inputs.
     """
@@ -213,6 +223,7 @@
     container = setup_test(bucket, container_test_name, options.skip_cleanup)
     test_share(container)
     test_autoserv(container)
+    test_package_install(container)
     logging.info('All tests passed.')