fix for CRM-12404 : "Supporter profile is not set for this Personal Camp...

- This part of issue raised due to removal of joomla frontend condition in file CRM/PCP/Form/PCPAccount.php during CRM-12111 issue fix (https://github.com/civicrm/civicrm-core/commit/254825102cec74c5679ba6dc56bc4ab1a3d883b7#diff-1).

- This condition was primarily coded for fixing a forum issue http://forum.civicrm.org/index.php/topic,17647.0/topicseen.html which seems to be a joomla specific issue.
  The patch coded for same is follows: https://fisheye2.atlassian.com/browse/CiviCRM/branches/v3.3/CRM/Contribute/Form/PCP/PCPAccount.php?r2=31560

Re-introducing the joomla frontend condition doesn't break CRM-12111 issue (in which it was removed). as well as solves the current issue.

NOTE: this is a part-1 fix for CRM-12404, for the second fix i filed a seperate pull request (https://github.com/civicrm/civicrm-wordpress/pull/14) which was against wordpress repo.