ofed_1_3/ofed_scripts: Add vendor script pre/post hooks for OFED install/uninstall

ofed_1_3/ofed_scripts: Add vendor script pre/post hooks for OFED install/uninstall

Vendors that distribute OFED sometimes need to add vendor specific
actions to the install and/or the uninstall process. This patch adds this
capability of adding scripts that would be executed before and after OFED
install and uninstall. Names of the scripts are given in the configuration
file for the install.pl script.

Examlpe (lines in ofed.conf)

vendor_pre_install=vendor_pre_install.sh
vendor_post_install=vendor_post_install.sh
vendor_pre_uninstall=vendor_pre_uninstall.sh
vendor_post_uninstall=vendor_post_uninstall.sh

Signed-off-by: Moni Shoua <monis@voltaire.com>