Reduce lock contention while updating caches

Use different locks for updating master and slave nodes caches .
Reduces lock contention and increases cache update performance when
using multiple slave nodes.
Traces updated
Merge pull request #19 from willemv/master

Added testcase for polling combined with merging to renamed modules
JENKINS-12829: A failed update sets revision of build to 000000+

The mercurial plugin ensures that a failed clone operation throws the
corresponding exception, but that's not the case if the subsequent
update fails: no check is done of the return code of the hg update
command.

The effect is that the revision of the build is set to 000000+, which
causes a huge change log calculation in the next build, as basically
the calculated log includes all thechange setss in the history of the
repo.
Export the Mercurial changeset number in addition to the node hash. Technically the names are the opposite of what they should be but REVISION was already used for the node id, so I didn't want to break backwards compatability

Signed-off-by: Geoff Lane <geoff@zorched.net>
updated maven pom to use repo.jenkins-ci.org repository
CRNL -> NL
Typos.
ciManagement
[maven-release-plugin] prepare release mercurial-1.39
[maven-release-plugin] prepare for next development iteration
Specifying license.
Merge https://github.com/jenkinsci/mercurial-plugin
Using 1.420 parent, as the first version to compile under JDK 7 [JENKINS-10490].
Factoring out testable method pathEquals.
[FIXED JENKINS-13400] Handle file:///path URLs.
updated maven pom to use repo.jenkins-ci.org repository
CRNL -> NL
Typos.
ciManagement