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

See osmo-ci change I2409b2928b4d7ebbd6c005097d4ad7337307dd93 for rationale.

Depends: I2409b2928b4d7ebbd6c005097d4ad7337307dd93
Change-Id: I9d35913f9cd60ff121d29f357919a0b0d62d6835
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index b08c63b..d159db9 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -14,8 +14,9 @@
 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]")
 
@@ -41,3 +42,5 @@
     $MAKE check || cat-testlogs.sh
     $MAKE distcheck || cat-testlogs.sh
 fi
+
+osmo-clean-workspace.sh