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

See osmo-ci change I2409b2928b4d7ebbd6c005097d4ad7337307dd93 for rationale.

Depends: I2409b2928b4d7ebbd6c005097d4ad7337307dd93
Change-Id: I7261e006163eda4bee8a4695fbd5bd29307babe6
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index cda0e2c..01e3da2 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -7,8 +7,9 @@
 inst="$deps/install"
 export deps inst
 
+osmo-clean-workspace.sh
+
 mkdir "$deps" || true
-rm -rf "$inst"
 
 verify_value_string_arrays_are_terminated.py $(find . -name "*.[hc]")
 
@@ -54,3 +55,5 @@
   || cat-testlogs.sh
 $MAKE distcheck \
   || cat-testlogs.sh
+
+osmo-clean-workspace.sh