Re-read auth-user-pass file on (re)connect if required

Re-read auth-user-pass file on (re)connect if required

Fixes trac #225 ('--auth-user-pass FILE' and '--auth-nocache' problem).

This patch is based on the changes suggested by ye_olde_iron in the trac
ticket.  Also added a note to the manpage to inform people to use
absolute paths when combining --auth-user-pass file and --auth-nocache.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1432386145-15045-1-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/9717
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit ac1cb5bfbb9e09e79fd737bc57999d968d77c5ad)