CI: Get job timeouts from environment

The job timeouts were hard coded in the jenkinsfiles which
means changes had to go through gerrit.  Now they are taken
from the following environment variables (and their defaults) that
can be set in Jenkins configuration...

TIMEOUT_GATES =      "60 MINUTES"
TIMEOUT_DAILIES =    "3 HOURS"
TIMEOUT_REF_DEBUG =  "24 HOURS"
TIMEOUT_UNITTESTS =  "30 MINUTES"

Change-Id: I673a551c1780bf665a3bc160b245da574aa4bbab

tests/CI/gates.jenkinsfile

@@ -10,10 +10,18 @@
  * we need to dynamically determine which docker image we're going to use and
  * you can't do that in a delcarative pipeline.
  */
+def timeoutTime = 60
+def timeoutUnits = 'MINUTES'
+if (env.TIMEOUT_GATES) {
+	def _timeout = env.TIMEOUT_GATES.split()
+	timeoutTime = _timeout[0].toInteger()
+	timeoutUnits = _timeout[1]
+}
+
 pipeline {
 	options {
 		timestamps()
-		timeout(time: 60, unit: 'MINUTES')
+		timeout(time: timeoutTime, unit: timeoutUnits)
 	}
 	triggers {
 		/*

tests/CI/periodics-daily.jenkinsfile

@@ -10,10 +10,18 @@
  * we need to dynamically determine which docker image we're going to use and
  * you can't do that in a delcarative pipeline.
  */
+def timeoutTime = 3
+def timeoutUnits = 'HOURS'
+if (env.TIMEOUT_DAILIES) {
+	def _timeout = env.TIMEOUT_DAILIES.split()
+	timeoutTime = _timeout[0].toInteger()
+	timeoutUnits = _timeout[1]
+}
+
 pipeline {
 	options {
 		timestamps()
-		timeout(time: 3, unit: 'HOURS')
+		timeout(time: timeoutTime, unit: timeoutUnits)
 	}
 	triggers {
 		cron 'H H(0-4) * * *'

tests/CI/ref_debug.jenkinsfile

@@ -10,10 +10,18 @@
  * we need to dynamically determine which docker image we're going to use and
  * you can't do that in a delcarative pipeline.
  */
+def timeoutTime = 24
+def timeoutUnits = 'HOURS'
+if (env.TIMEOUT_REF_DEBUG) {
+	def _timeout = env.TIMEOUT_REF_DEBUG.split()
+	timeoutTime = _timeout[0].toInteger()
+	timeoutUnits = _timeout[1]
+}
+
 pipeline {
 	options {
 		timestamps()
-		timeout(time: 1, unit: 'DAYS')
+		timeout(time: timeoutTime, unit: timeoutUnits)
 	}
 	triggers {
 		cron 'H H(0-4) * * 0'

tests/CI/unittests.jenkinsfile

@@ -10,10 +10,18 @@
  * we need to dynamically determine which docker image we're going to use and
  * you can't do that in a delcarative pipeline.
  */
+def timeoutTime = 30
+def timeoutUnits = 'MINUTES'
+if (env.TIMEOUT_UNITTESTS) {
+	def _timeout = env.TIMEOUT_UNITTESTS.split()
+	timeoutTime = _timeout[0].toInteger()
+	timeoutUnits = _timeout[1]
+}
+
 pipeline {
 	options {
 		timestamps()
-		timeout(time: 30, unit: 'MINUTES')
+		timeout(time: timeoutTime, unit: timeoutUnits)
 	}
 	triggers {
 		/*