qa/workunits/cephtool: check_response didn't find erasure-code string

qa/workunits/cephtool: check_response didn't find erasure-code string

1. If data or metadata pool is already in-use by filesystem
then it is not allowed to reuse the same pool for another
filesystems.

2. Test is failing because above(1) restrictions/checks comes
before checking erasure-code pools. Hence test is failing
and not finding expected error string in output.

3. Proposed fix checks newly added error string instead of
'erasure-code'.

4. Also adding new tests to verify string 'erasure-code'
by passing --force option so that check for pools reuse(1)
will be skipped and check for 'erasure-code' will be hit.

Fixes: https://tracker.ceph.com/issues/56384
Signed-off-by: Nikhilkumar Shelke <nshelke@redhat.com>