userspace/snmpd: change order of branches in MIB

No technical change.

Change location of branch wrSwitchMIB.wrsStatus from high number (256) to
low (6), then move wrSwitchMIB.wrsEpertStatus to (7).
At the beginning wrsStatus branch was placed at high number because objects
from that branch might use several other objects to calculate their own value.
For example, there was a risk that query of wrsMainSystemStatus triggers
cascade of time consuming cache fills and snmpget timeouts. However, practice
shown that cache filling is significantly shorter that SNMP transfers.
Additionally, such risk was possible in case of snmpwalk or other method
querying objects in order.
Signed-off-by: Adam Wujek <adam.wujek@cern.ch>