Fixed pam_pbssimpleauth.c to accept jobdir=<jobdir>

If 'jobdir' is specified in pam configuration, pam_pbssimpleauth.c previously copied the string 'jobdir' over the compile-time default value of PBS_SERVER_HOME '/mom_priv/jobs'.

This change fixes it to copy the path part of a 'jobdir=<path to jobs>' pam configuration option in, for example, /etc/pam.d/password-auth, of the form:

account     required      pam_pbssimpleauth.so jobdir=/var/spool/torque/mom_priv/jobs