'pre-scm-buildstep' wrapper has two modes:
1. Older: no 'buildsteps' element is specified. Build steps is a list under
wrapper name. For example:
- pre-scm-buildstep:
- shell: echo hello
- shell: echo bye
2. Newer: build steps specified inside 'buildsteps' mapping element:
- pre-scm-buildsteps:
buildsteps:
- shell: echo hello
- shell: echo bye
But, when 'preSCMbuildstep' plugin version is equal or higher 0.3, and first
mode is used, it fails.
Fix that.
Change-Id: I010d9f6c5e06ccd8c2723026aae2c60f79917ff4
e2cf69b4f4