Don't start reload timer if a timer is already running

[bjoernricks]

Avoid running multiple timers for the same page. This could happen
before when changing the filter while a timer was running.

Checklist:

• [n/a] Tests
• CHANGES Entry

[codecov]

Codecov Report

Merging #1289 into gsa-8.0 will decrease coverage by 0.02%.
The diff coverage is 0%.

@@             Coverage Diff             @@
##           gsa-8.0    #1289      +/-   ##
===========================================
- Coverage    18.08%   18.05%   -0.03%     
===========================================
  Files          953      953              
  Lines        27723    27689      -34     
  Branches      6006     5985      -21     
===========================================
- Hits          5013     4999      -14     
+ Misses       21303    21285      -18     
+ Partials      1407     1405       -2

Impacted Files	Coverage Δ
gsa/src/web/entity/container.js	0% <0%> (ø)	⬆️
gsa/src/web/entities/container.js	0% <0%> (ø)	⬆️
gsa/src/web/pages/reports/detailspage.js	0% <0%> (ø)	⬆️
gsa/src/web/entities/table.js	0% <0%> (ø)	⬆️
gsa/src/web/pages/reports/listpage.js	0% <0%> (ø)	⬆️
gsa/src/gmp/models/filter/convert.js	100% <0%> (ø)	⬆️
gsa/src/gmp/models/filter.js	100% <0%> (ø)	⬆️
gsa/src/web/components/powerfilter/powerfilter.js	0% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 8ac1e5b...b249481. Read the comment docs.