jailsetup.sh: create initial .gitconfig

jailsetup.sh: create initial .gitconfig

If there is no $chroot/etc/girocco/.gitconfig (or it's empty)
create an initial one that contains global settings to use whenever
Girocco runs a git command.

Initially start off with http.lowSpeedLimit=1 and http.lowSpeedTime=600
so that http activity will automatically time out after 10 minutes of
no response.  Even cloning blink without pack bitmaps using --quiet with
a version of Git prior to 1.8.4.2 only takes just over 5 minutes to
start sending objects, so 10 minutes should be more than enough.  Besides
which some servers have a default timeout of 5 minutes anyway that
would trigger before the 10 minutes is up.

+[http]
+	lowSpeedLimit = 1
+	lowSpeedTime = 600