paths: have one common parent dir /var/tmp/osmo-gsm-tester

In the example config and the jenkins scripts, use paths below common parent
dir /var/tmp/osmo-gsm-tester.

1. example: put the state dir in /var/tmp/osmo-gsm-tester/state, instead of in
the config dir like /etc/osmo-gsm-tester.

2. contrib scripts: place trials in /var/tmp/osmo-gsm-tester/trials, and to
move into place atomically, use /var/tmp/osmo-gsm-tester/.prep-trials as
temporary location.

The OsmoGSMTester manual is currently also being updated to setup these paths,
with /var/tmp/osmo-gsm-tester owned by a common group and having group-sticky
as well has group-writable access rules.

Change-Id: I2961e9d1d9b14859b886058b54ffcb36f4d88bc1
diff --git a/example/paths.conf b/example/paths.conf
index 3458a1d..554d942 100644
--- a/example/paths.conf
+++ b/example/paths.conf
@@ -1,3 +1,3 @@
-state_dir: './state'
+state_dir: '/var/tmp/osmo-gsm-tester/state'
 suites_dir: '../suites'
 scenarios_dir: './scenarios'