LU-14748 build: gcc9 fix address of packed member warning

LU-14748 build: gcc9 fix address of packed member warning

gcc9 complains about use of __swabXXs() with some packed
structures.
Use __swabXX() for these cases.

Test-Parameters: trivial
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I7437c6f21d38c209ef452b41760aad6d1d3d6034
Reviewed-on: https://review.whamcloud.com/43961
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>