Current implementation of Multiple SCMs Plugin seems to be broken. Test
with following combination of Jenkins and Multiple SCMs Plugin
* Jenkins 2.2 (latest) + multiple-scms 0.6 (latest)
* Jenkins 1.651.1 (latest LTS) + multiple-scms 0.6 (latest)
* Jenkins 1.409.1 (oldest LTS) + multiple-scms 0.1 (oldest)
* Jenkins 1.396 (oldest) + multiple-scms 0.1 (oldest)
all emitted XML with following format (apart from `plugin=` here and
there):
```
<scm class="org.jenkinsci.plugins.multiplescms.MultiSCM">
<scms>
<hudson.scm.SubversionSCM>
:
</hudson.scm.SubversionSCM>
<hudson.scm.CVSSCM>
:
</hudson.scm.CVSSCM>
</scms>
</scm>
```
whereas current Jenkins Job Builder implementation emits XML with
following format:
```
<scm class="org.jenkinsci.plugins.multiplescms.MultiSCM">
<scms>
<scm class="hudson.scm.SubversionSCM">
:
</scm>
<scm class="hudson.scm.CVSSCM">
:
</scm>
</scms>
</scm>
```
This commit will fix this problem by modifying child `scm` node to a
correct format before adding to the parent `scm` node.
Change-Id: I0b9115c156a06a7fbdf529341dfc6100edf225aa
Signed-off-by: Ryo Tagami <rtagami@airstrip.jp>