jenkins: use osmo-clean-workspace.sh before and after build
jenkins: use osmo-clean-workspace.sh before and after build

See osmo-ci change I2409b2928b4d7ebbd6c005097d4ad7337307dd93 for rationale.

Depends: I2409b2928b4d7ebbd6c005097d4ad7337307dd93
Change-Id: I609f7c7c88b49f26e2e48e1f1cffed76d9e6fb5e

ttsou/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,ttsou/osmo-trx,ttsou/osmo-trx,osmocom/osmo-trx,osmocom/osmo-trx