LU-13944 tests: add ability to set clients parameters

Patch adds the ability to set clients parameters via
CLIENT_LCTL_SETPARAM_PARAM.
Example:
  CLIENT_LCTL_SETPARAM_PARAM="lbug_on_eviction=1 debug=-1 "
sets lbug_on_eviction=1 and debug=-1 on all clients.

Test-Parameters: trivial
HPE-bug-id: LUS-9052
Signed-off-by: Elena Gryaznova <elena.gryaznova@hpe.com>
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Reviewed-by: Andriy Skulysh <c17819@cray.com>
Change-Id: Ifb06e7992c2f1db94f0a1503cfc31e00d4674804
Reviewed-on: https://review.whamcloud.com/39816
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>