Fix contrib/sepgsql test policy to work with latest SELinux releases.

As of Fedora 30, it seems that the system-provided macros for setting
up user privileges in SELinux policies don't grant the ability to read
/etc/passwd, as they formerly did.  This restriction breaks psql
(which tries to use getpwuid() to obtain the user name it's running
under) and thereby the contrib/sepgsql regression test.  Add explicit
specifications that we need the right to read /etc/passwd.

Mike Palmiotto, per a report from me.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/23856.1563381159@sss.pgh.pa.us

contrib/sepgsql/sepgsql-regtest.te

@@ -31,6 +31,9 @@ userdom_base_user_template(sepgsql_regtest_superuser)
 userdom_manage_home_role(sepgsql_regtest_superuser_r, sepgsql_regtest_superuser_t)
 userdom_exec_user_home_content_files(sepgsql_regtest_superuser_t)
 userdom_write_user_tmp_sockets(sepgsql_regtest_superuser_t)
+
+auth_read_passwd(sepgsql_regtest_superuser_t)
+
 optional_policy(`
 	postgresql_stream_connect(sepgsql_regtest_superuser_t)
 	postgresql_unconfined(sepgsql_regtest_superuser_t)
@@ -60,6 +63,9 @@ userdom_base_user_template(sepgsql_regtest_dba)
 userdom_manage_home_role(sepgsql_regtest_dba_r, sepgsql_regtest_dba_t)
 userdom_exec_user_home_content_files(sepgsql_regtest_dba_t)
 userdom_write_user_tmp_sockets(sepgsql_regtest_user_t)
+
+auth_read_passwd(sepgsql_regtest_dba_t)
+
 optional_policy(`
 	postgresql_admin(sepgsql_regtest_dba_t, sepgsql_regtest_dba_r)
 	postgresql_stream_connect(sepgsql_regtest_dba_t)
@@ -98,6 +104,9 @@ userdom_base_user_template(sepgsql_regtest_user)
 userdom_manage_home_role(sepgsql_regtest_user_r, sepgsql_regtest_user_t)
 userdom_exec_user_home_content_files(sepgsql_regtest_user_t)
 userdom_write_user_tmp_sockets(sepgsql_regtest_user_t)
+
+auth_read_passwd(sepgsql_regtest_user_t)
+
 optional_policy(`
 	postgresql_role(sepgsql_regtest_user_r, sepgsql_regtest_user_t)
 	postgresql_stream_connect(sepgsql_regtest_user_t)
@@ -126,6 +135,8 @@ userdom_manage_home_role(sepgsql_regtest_pool_r, sepgsql_regtest_pool_t)
 userdom_exec_user_home_content_files(sepgsql_regtest_pool_t)
 userdom_write_user_tmp_sockets(sepgsql_regtest_pool_t)
 
+auth_read_passwd(sepgsql_regtest_pool_t)
+
 type sepgsql_regtest_foo_t;
 type sepgsql_regtest_var_t;
 type sepgsql_regtest_foo_table_t;