EX-4265 lipe: fix automated lpurge configuration

EX-4265 lipe: fix automated lpurge configuration

In stratagem-hp-config.sh, delay setting LPURGE_FREEHI until the
automatic values have been determined.

Test-Parameters: trivial
Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I3042061cf0f2da8e807a3ed2acc527cb9517385b
Reviewed-on: https://review.whamcloud.com/45810
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Gaurang Tapase <gtapase@ddn.com>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/46128