fix CGRefundBuild to release build properly

CGInitBuild will fail on already existing build (even canceled/failed),
so it can't be used to reuse previously refunded nvr.

CGRefund build doesn't delete reservation. Having reservation token for
build which is no more in BUILDING doesn't make much sense and blocks
and reservation of same NVR.

Fixes: https://pagure.io/koji/issue/1852

hub/kojihub.py

@@ -5809,7 +5809,7 @@ def cg_init_build(cg, data):
     data['cg_id'] = cg_id
     # CGs shouldn't have to worry about epoch
     data.setdefault('epoch', None)
-    build_id = new_build(data, strict=True)
+    build_id = new_build(data, strict=False)
     # store token
     token = generate_token()
     insert = InsertProcessor(table='build_reservations')
@@ -5855,6 +5855,7 @@ def cg_refund_build(cg, build_id, token, state=koji.BUILD_STATES['FAILED']):
     binfo = get_build(build_id, strict=True)
     koji.plugin.run_callbacks('postBuildStateChange', attribute='state',
                               old=koji.BUILD_STATES['BUILDING'], new=state, info=binfo)
+    clear_reservation(build_id)
 
 
 def cg_import(metadata, directory, token=None):