LU-11607 tests: replace lustre_version calls in sanity-flr/pfl

LU-11607 tests: replace lustre_version calls in sanity-flr/pfl

The routine get_lustre_env() is available to all Lustre test
suites and sets an environment variable for the Lustre
version of servers for MDS1.

In sanity-flr and sanity-pfl, replace the calls to
lustre_version_code() for all server types with
definitions in get_lustre_env().

While doing this, replace ‘lustre_version_code $SINGLEMDS’
with ‘MDS1_VERSION’.

Clean up around any modifications by removing calls to
return after skip() or skip_env().

Test-Parameters: trivial testlist=sanity-flr,sanity-pfl
Test-Parameters: fstype=zfs testlist=sanity-flr,sanity-pfl
Signed-off-by: James Nunez <jnunez@whamcloud.com>
Change-Id: Ic80ea80268ba28f52d96680e304838b6e8c3a6fd
Reviewed-on: https://review.whamcloud.com/35760
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>