IMPALA-7329: Blacklist CDH Maven snapshots repository
IMPALA-7329: Blacklist CDH Maven snapshots repository

The Impala development bootstrapping depends on CDH Maven snapshots
which transitively pull dependencies from other repositories which
can cause the build to be non-reproducible, e.g. IMPALA-7316. This
patch makes the build to be reproducible by blacklisting
cdh.snapshots.repo so that Maven does not accidentally downloads the
latest CDH snapshots when running a build, which can cause
incompatibility issues.

Testing:
- Ran core tests with CDH_BUILD_NUMBER=422770 and did not hit the
  issue described in IMPALA-7316

Change-Id: Id945bc2769f92f3df3bb4f617b00db77a6502ff3
Reviewed-on: http://gerrit.cloudera.org:8080/10999
Reviewed-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>
Tested-by: Impala Public Jenkins <039b6b20426ff68ebe492b3021890d8c8fd010c9@cloudera.com>

cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala,cloudera/Impala