IMPALA-2761: Use gutil/walltime for platform independent monotonic clock
IMPALA-2761: Use gutil/walltime for platform independent monotonic clock

In absence of C++11 use gutil's walltime module to handle platform
independent monotonic clock operations.

Change-Id: Ic6b8593ffbd298c612a11ace38da9fc50aaa02bd
Reviewed-on: http://gerrit.cloudera.org:8080/1611
Reviewed-by: Martin Grund <2546548d516fa64c411fde8242af35f3f80ad31f@cloudera.com>
Readability: Martin Grund <2546548d516fa64c411fde8242af35f3f80ad31f@cloudera.com>
Tested-by: Internal Jenkins

kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala,kapilrastogi/Impala