mpi_t: Remove invalid error check

MPL_env2str is used to check for CVARs with string or enum type. It
returns only 0 or 1 based on whether the environment variable is
found. It never returns -1, so we can safely remove the error check.

Author: raffenet

maint/extractcvars

@@ -340,7 +340,6 @@ EOT
         elsif ($p->{type} eq 'string' or $p->{type} eq 'enum') {
 print OUTPUT_C <<EOT;
     rc = MPL_env2${env_fn}("$env_name", &tmp_str);
-    MPIR_ERR_CHKANDJUMP1((-1 == rc),mpi_errno,MPI_ERR_OTHER,"**envvarparse","**envvarparse %s","$env_name");
     got_rc += rc;
 EOT
         }