There where a number of places where the zone table should have
been locked, but wasn't, when dns_zt_apply was called.
Added a isc_rwlocktype_t type parameter to dns_zt_apply and adjusted
all calls to using it. Removed locks in callers.
Backported and modified upstream commit e5068a7e24d7ace5ed7e8fdd3ff789dcc4c10fe8
Resolves: rhbz#2101712
