migrate to new mgm_address and mgm_name functions

Fix #109 (closed)

IMPORTANT NOTE: requires no-MQ mode.

• replace utils.mgm_hostname with new function utils.mgm_name
  • utils.mgm_name also replaces the mgm.fullname function which was similar to, and likely redundant with utils.mgm_hostname - the type of inconsistency this MR addresses.
  • Changing mgm.fullname to utils.mgm_name is a fully self-contained change within the mgm/ sub-chart that can not have any effect - except for possibly external references to the MGM service name, which is another inconsistency this MR addresses.
• replace utils.mgm_fqdn with new function utils.mgm_address
• remove *ofs.broker settings that point to the MQ port
• add new value .Values.global.mgm_name to customize short name of the MGM service if needed

POTENTIALLY BREAKING CHANGE: in order to address #109 (closed) it is necessary to eliminate the complicated logical configuration paths of the old functions, and the numerous layers of variables that can override them in different ways, with simple new functions, with a single variable .Values.global.mgm_name that can be used to customize the short name of the MGM service. For typical installations using sane default values, the chart will continue working normally and no change will be required to upgrade. However installations that are making use of the complex logic to override the defaults will need to set the new value .Values.global.mgm_name to an appropriate string to ensure that the MGM service still has the desired name.