Set dynamicTriggerConfiguration switch

In Jenkins version 1.490 with Gerrit Trigger plugin
1.6.0 the dynamicTriggerConfiguration flag
needs to be explicitly turned off in order for the
triggers defined within the job to work properly.

Change-Id: If5835e933b812a7fe17c49f0f6988360f7154f80
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Do not assume a failure message is specified

Not everyone needs a custom failure message, so
if nothing is specified create an empty node.

Change-Id: I82f69e28574c01cbc6de649f968482352f42b8d8
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>
Add an option for the buildChooser

Depending on what plugins are installed, the user may want
to specify a different "chooser strategy" via the buildChooser
field. Add an option for doing so.

Change-Id: Iba59f8c0a8446c88f64ed8b70b3639a89d9b9ef0
Signed-off-by: Doug Hellmann <doug.hellmann@dreamhost.com>