packaging: spec: update spec syntax

Solves:
 ***************************************************************
 * WARNING!  mvn-rpmbuild is deprecated and it will be removed *
 * in future.  Users should migrate to using %mvn_build macro  *
 * or call XMvn directly if greater flexibility is required.   *
 ***************************************************************

Change-Id: Ib81f345772db5da4d23cf1ee917b3d11e85b3ed6
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>