git-p4: do not pass '-r 0' to p4 commands

git-p4: do not pass '-r 0' to p4 commands

git-p4 crashes when used with a very old p4 client version
that does not support the '-r <number>' option in its commands.

Allow making git-p4 work with old p4 clients by setting git-p4.retries to 0.

Alternatively git-p4.retries could be made opt-in.
But since only very old, barely maintained p4 versions don't support
the '-r' option, the setting-retries-to-0 workaround would do.

The "-r retries" option is present in Perforce 2012.2 Command Reference,
but absent from Perforce 2012.1 Command Reference.

Signed-off-by: Igor Kushnir <igorkuo@gmail.com>
Acked-by: Lars Schneider <larsxschneider@gmail.com>
Reviewed-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>