LU-13169 tests: quiet debug messages during tests

LU-13169 tests: quiet debug messages during tests

Quiet the output of check_network() and check_node_health() that are
printed for *every* subtest that is run, since this is distracting
when looking at the test output, and can often be more verbose than
the actual test output.

Don't get the client and server versions repeatedly, since they will
not change for the duration of a test run and can be cached instead.

Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: Ib42b01c9ca36c6c72d2c7ffffbd3a5f2643ebbe5
Reviewed-on: https://review.whamcloud.com/37338
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>