LU-14272 tests: different mpirun options for different users

LU-14272 tests: different mpirun options for different users

Patch adds the ability to use different mpirun options for
different mpi users, for example we use:
  --wdir=/home/quota15_1 for user quota15_1
and
  --wdir=/home/quota15_2 for user quota15_2.

Per mpi user option can be specified after ':' in ha_mpi_users:
Example:
  ha_mpi_users="quota15_1:--wdir=/home/quota15_1
                quota15_2:--wdir=/home/quota15_2
                quota15_3
                quota15_4:--wdir=/home/quota15_4"
Several options for user  can be set as:
  ha_mpi_users="user1:<option11>
                user1:<option12>
                user2:<option21>"
MPIRUN_OPTIONS will be applied for all users.

Patch adds the ability to execute the command before loads start.
Example: ha_precmd="for i in 1 2 3 4; do
                lfs quota -v -u quota15_$i $ha_test_dir; done"

Test-Parameters: trivial
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
HPE-bug-id: LUS-9069
Reviewed-by: Vladimir Saveliev <vladimir.saveliev@hpe.com>
Reviewed-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Change-Id: I35feadcc856dbc3d6d6d5f2720ab49c6c111161b
Reviewed-on: https://review.whamcloud.com/41072
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>