rhel6: selinux boolean "use_nfs_home_dirs" should allow "automount_tmp_t:dir search"

Issue

• we're using nfs(3) home directories in combination with RHEL6
• the use_nfs_home_dirs boolean is on.
• this boolean allows sshd and xauth access to nfs_t files, which happens to be the type for a users home directory.
• however we still had issues with selinux blocking sshd from reading public keys and xauth from creating .Xauthority files
• analysis of the avc messages (after disabling the dont-audit rules) shows that sshd and xauth are blocked access to automount_tmp_t
• It turns out that during the login process the home directory transitiones from automount_tmp_t to nfs_t