ktest: Add PRE_INSTALL option

Add the PRE_INSTALL option that will allow a user to specify a shell
command to be executed before the install operation executes.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/tools/testing/ktest/sample.conf b/tools/testing/ktest/sample.conf
index 4472452..19754e0 100644
--- a/tools/testing/ktest/sample.conf
+++ b/tools/testing/ktest/sample.conf
@@ -426,6 +426,14 @@
 # (default "")
 #BUILD_OPTIONS = -j20
 
+# If you need to do some special handling before installing
+# you can add a script with this option.
+# The environment variable KERNEL_VERSION will be set to the
+# kernel version that is used.
+#
+# default (undefined)
+#PRE_INSTALL = ssh user@target rm -rf '/lib/modules/*-test*'
+
 # If you need an initrd, you can add a script or code here to install
 # it. The environment variable KERNEL_VERSION will be set to the
 # kernel version that is used. Remember to add the initrd line