EX-3720 tests: skip lpcc_purge tests if not installed

EX-3720 tests: skip lpcc_purge tests if not installed

Skip lpcc_purge tests if package is not installed on client.

Test-Parameters: trivial testlist=sanity-pcc env=ONLY=200-202                  clientextra_install_params="--packages lipe-lpcc"
Test-Parameters: testlist=sanity-pcc env=ONLY=200-202
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ic977c1cad602cc1ae33b273493bfb9d0f9dbe37b
Reviewed-on: https://review.whamcloud.com/44994
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>