Don't skip the cleanup call if a pager object is marked as blocked.
It happens that the pager_object is in destruction but it is also used
concurrently by the pager thread. The pager thread handling code may set the
pager object to blocked but still uses the pointer to the pager object. Avoid
locking at the state of the pager object and make the cleanup call everytime.
Error output looks like this, where the pf_ip is within
void Pager_object::_page_fault_handler(addr_t pager_obj)
method and the pf_addr is the stale pointer to the already released pager_object.
no RM attachment (READ pf_addr=xxx pf_ip=xxx from 00 <NULL>)
static void Genode::Pager_object::_page_fault_handler(Genode::addr_t): page fault, thread '<NULL>', cpu x, ip=xxx, fault address=xxx
PAGE-FAULT IN CORE (READ pf_addr=b10e0090 pf_ip=132dbc from 00 <NULL>)
ceb04d3c11