staging: lustre: remove l_wait_event from ptlrpc_set_wait

This is the last remaining use of l_wait_event().
It is the only use of LWI_TIMEOUT_INTR_ALL() which
has a meaning that timeouts can be interrupted.
Only interrupts by "fatal" signals are allowed, so
introduce l_wait_event_abortable_timeout() to
support this.

Reviewed-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Patrick Farrell <paf@cray.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>